diff --git a/effdet/data/dataset.py b/effdet/data/dataset.py
index d7515622..48a12ec7 100644
--- a/effdet/data/dataset.py
+++ b/effdet/data/dataset.py
@@ -2,11 +2,14 @@
 
 Hacked together by Ross Wightman
 """
+
 import torch.utils.data as data
 import numpy as np
+import os
 
 from PIL import Image
 from .parsers import create_parser
+from .mosaic_augmentation import MosaicAugmentation
 
 
 class DetectionDatset(data.Dataset):
@@ -18,9 +21,9 @@ class DetectionDatset(data.Dataset):
 
     """
 
-    def __init__(self, data_dir, parser=None, parser_kwargs=None, transform=None):
+    def __init__(self, data_dir, parser=None, mosaic=False, parser_kwargs=None, transform=None):
         super(DetectionDatset, self).__init__()
-        parser_kwargs = parser_kwargs or {}
+        parser_kwargs = parser_kwargs or {}  
         self.data_dir = data_dir
         if isinstance(parser, str):
             self._parser = create_parser(parser, **parser_kwargs)
@@ -28,7 +31,7 @@ def __init__(self, data_dir, parser=None, parser_kwargs=None, transform=None):
             assert parser is not None and len(parser.img_ids)
             self._parser = parser
         self._transform = transform
-
+        self.mosaic = mosaic 
     def __getitem__(self, index):
         """
         Args:
@@ -36,14 +39,26 @@ def __getitem__(self, index):
         Returns:
             tuple: Tuple (image, annotations (target)).
         """
+
+        
         img_info = self._parser.img_infos[index]
         target = dict(img_idx=index, img_size=(img_info['width'], img_info['height']))
         if self._parser.has_labels:
             ann = self._parser.get_ann_info(index)
             target.update(ann)
+            
 
         img_path = self.data_dir / img_info['file_name']
         img = Image.open(img_path).convert('RGB')
+        if "train" in os.fsdecode(self.data_dir) and self.mosaic:
+            mosaic_augmentation = MosaicAugmentation(index,
+                                                     self._parser,
+                                                     self.data_dir)
+            img, bboxes, classes, img_size = mosaic_augmentation()
+            target.update(
+                img_size=(img_size, img_size), bbox=bboxes, cls=classes)
+
+
         if self.transform is not None:
             img, target = self.transform(img, target)
 
diff --git a/effdet/data/dataset_factory.py b/effdet/data/dataset_factory.py
index d47e183b..86a6ca64 100644
--- a/effdet/data/dataset_factory.py
+++ b/effdet/data/dataset_factory.py
@@ -12,7 +12,7 @@
 from .parsers import create_parser
 
 
-def create_dataset(name, root, splits=('train', 'val')):
+def create_dataset(name, root, splits=('train', 'val'), mosaic=False):
     if isinstance(splits, str):
         splits = (splits,)
     name = name.lower()
@@ -36,6 +36,7 @@ def create_dataset(name, root, splits=('train', 'val')):
             datasets[s] = dataset_cls(
                 data_dir=root / Path(split_cfg['img_dir']),
                 parser=create_parser(dataset_cfg.parser, cfg=parser_cfg),
+                mosaic=mosaic
             )
     elif name.startswith('voc'):
         if 'voc0712' in name:
diff --git a/effdet/data/mosaic_augmentation.py b/effdet/data/mosaic_augmentation.py
new file mode 100644
index 00000000..eb0863f6
--- /dev/null
+++ b/effdet/data/mosaic_augmentation.py
@@ -0,0 +1,297 @@
+import random
+import math
+import torch
+import numpy as np
+import cv2
+from PIL import Image
+import os
+
+
+class MosaicAugmentation:
+    """Randomly selects 3 other training images to form a 4 tiled image, with
+        different aspect ratios. Original implementation from
+        https://github.com/ultralytics/yolov5
+        with slight changes to fit this codebase.
+    Args:
+        index: Current image to be transformed
+        parser: Parser to obtain annotations from images
+        degrees: image rotation (deg)
+        translate: image translation (deg)
+        scale: image scale
+        shear: image shear
+        perspective: image perspective(+/- fraction)
+    """
+
+    def __init__(
+        self,
+        index,
+        parser,
+        data_dir,
+        img_size=640,
+        degrees=0.0,
+        translate=0.1,
+        scale=0.5,
+        shear=0.0,
+        perspective=0.0,
+    ):
+        self.index = index
+        self._parser = parser
+        self.data_dir = data_dir
+        self.img_size = img_size
+        self.degrees = degrees
+        self.translate = translate
+        self.scale = scale
+        self.shear = shear
+        self.perspective = perspective
+        self.mosaic_border = [-self.img_size // 2, -self.img_size // 2]
+        self.indices = range(0, len(self._parser.img_ids))
+        self.augment = True
+
+    def __call__(self):
+        # loads images in a 4-mosaic
+        annotations4 = []
+        s = self.img_size
+        yc, xc = [
+            int(random.uniform(-x, 2 * s + x)) for x in self.mosaic_border
+        ]  # mosaic center x, y
+        indices = [self.index] + random.choices(
+            self.indices, k=3
+        )  # 3 additional image indices
+        for i, index in enumerate(indices):
+            # Load image
+            img, _, (h, w) = load_image(self, index)
+
+            # place img in img4
+            if i == 0:  # top left
+                img4 = np.full(
+                    (s * 2, s * 2, img.shape[2]), 114, dtype=np.uint8
+                )  # base image with 4 tiles
+                x1a, y1a, x2a, y2a = (
+                    max(xc - w, 0),
+                    max(yc - h, 0),
+                    xc,
+                    yc,
+                )  # xmin, ymin, xmax, ymax (large image)
+                x1b, y1b, x2b, y2b = (
+                    w - (x2a - x1a),
+                    h - (y2a - y1a),
+                    w,
+                    h,
+                )  # xmin, ymin, xmax, ymax (small image)
+            elif i == 1:  # top right
+                x1a, y1a, x2a, y2a = xc, max(yc - h, 0), min(xc + w, s * 2), yc
+                x1b, y1b, x2b, y2b = 0, h - (y2a - y1a), min(w, x2a - x1a), h
+            elif i == 2:  # bottom left
+                x1a, y1a, x2a, y2a = max(xc - w, 0), yc, xc, min(s * 2, yc + h)
+                x1b, y1b, x2b, y2b = w - (x2a - x1a), 0, w, min(y2a - y1a, h)
+            elif i == 3:  # bottom right
+                x1a, y1a, x2a, y2a = (
+                    xc,
+                    yc,
+                    min(xc + w, s * 2),
+                    min(s * 2, yc + h),
+                )
+                x1b, y1b, x2b, y2b = 0, 0, min(w, x2a - x1a), min(y2a - y1a, h)
+
+            img4[y1a:y2a, x1a:x2a] = img[
+                y1b:y2b, x1b:x2b
+            ]  # img4[ymin:ymax, xmin:xmax]
+            padw = x1a - x1b
+            padh = y1a - y1b
+
+            # Labels
+            ann = self._parser.get_ann_info(index)
+            annotations = np.zeros((len(ann["bbox"]), 5))
+            # print("Ann Bbox", ann['bbox'])
+            # print("ann cls", ann['cls'])
+            for idx, bbox in enumerate(ann["bbox"]):
+                bb = list(bbox.copy())
+                cls = [ann["cls"][idx]]
+                bb = cls + bb
+                annotations[idx] = bb
+
+            if self._parser.yxyx:
+                annotations[:, 0:5] = annotations[:, [0, 2, 1, 4, 3]]  # to xyxy
+
+            if annotations.size:
+                annotations[:, 1:] = add_padding(annotations[:, 1:], padw, padh)
+            annotations4.append(annotations)
+
+        # Concat/clip annotations
+        annotations4 = np.concatenate(annotations4, 0)
+        for x in annotations4[:, 1:]:
+            np.clip(x, 0, 2 * s, out=x)  # clip when using random_perspective()
+        # img4, annotations4 = replicate(img4, annotations4)  # replicate
+
+        # Augment
+        img4, annotations4 = random_perspective(
+            img4,
+            annotations4,
+            degrees=self.degrees,
+            translate=self.translate,
+            scale=self.scale,
+            shear=self.shear,
+            perspective=self.perspective,
+            border=self.mosaic_border,
+        )  # border to remove
+
+        annotations4[:, 0:5] = (
+            annotations4[:, [0, 2, 1, 4, 3]]
+            if self._parser.yxyx
+            else annotations4
+        )
+        classes = annotations4[:, 0]
+        bboxes = annotations4[:, 1:5]
+        img = cv2.cvtColor(img4, cv2.COLOR_BGR2RGB)
+        img_pil4 = Image.fromarray(img)
+        return img_pil4, bboxes, classes, self.img_size
+
+
+def load_image(self, index):
+    img_info = self._parser.img_infos[index]
+    img_path = self.data_dir / img_info["file_name"]
+    img = cv2.imread(os.fsdecode(img_path))  # BGR
+    assert img is not None, "Image Not Found " + img_path
+    h0, w0 = img.shape[:2]  # orig hw
+    r = self.img_size / max(h0, w0)  # ratio
+    if r != 1:  # if sizes are not equal
+        img = cv2.resize(
+            img,
+            (int(w0 * r), int(h0 * r)),
+            interpolation=cv2.INTER_AREA
+            if r < 1 and not self.augment
+            else cv2.INTER_LINEAR,
+        )
+    return img, (h0, w0), img.shape[:2]  # img, hw_original, hw_resized
+
+
+def box_candidates(
+    box1, box2, wh_thr=2, ar_thr=20, area_thr=0.1, eps=1e-16
+):  # box1(4,n), box2(4,n)
+    # Compute candidate boxes: box1 before augment, box2 after augment,
+    # wh_thr (pixels), aspect_ratio_thr, area_ratio
+    w1, h1 = box1[2] - box1[0], box1[3] - box1[1]
+    w2, h2 = box2[2] - box2[0], box2[3] - box2[1]
+    ar = np.maximum(w2 / (h2 + eps), h2 / (w2 + eps))  # aspect ratio
+    return (
+        (w2 > wh_thr)
+        & (h2 > wh_thr)
+        & (w2 * h2 / (w1 * h1 + eps) > area_thr)
+        & (ar < ar_thr)
+    )  # candidates
+
+
+def add_padding(x, padw, padh):
+    y = x.clone() if isinstance(x, torch.Tensor) else np.copy(x)
+    y[:, 0] = x[:, 0] + padw
+    y[:, 1] = x[:, 1] + padh
+    y[:, 2] = x[:, 2] + padw
+    y[:, 3] = x[:, 3] + padh
+    return y
+
+
+def random_perspective(
+    img,
+    targets=(),
+    degrees=10,
+    translate=0.1,
+    scale=0.1,
+    shear=10,
+    perspective=0.0,
+    border=(0, 0),
+):
+    # torchvision.transforms.RandomAffine(degrees=(-10, 10), translate=(.1, .1)
+    # , scale=(.9, 1.1), shear=(-10, 10))
+    # targets = [cls, xyxy]
+
+    height = img.shape[0] + border[0] * 2  # shape(h,w,c)
+    width = img.shape[1] + border[1] * 2
+
+    # Center
+    C = np.eye(3)
+    C[0, 2] = -img.shape[1] / 2  # x translation (pixels)
+    C[1, 2] = -img.shape[0] / 2  # y translation (pixels)
+
+    # Perspective
+    P = np.eye(3)
+    P[2, 0] = random.uniform(
+        -perspective, perspective
+    )  # x perspective (about y)
+    P[2, 1] = random.uniform(
+        -perspective, perspective
+    )  # y perspective (about x)
+
+    # Rotation and Scale
+    R = np.eye(3)
+    a = random.uniform(-degrees, degrees)
+    # a += random.choice([-180, -90, 0, 90])
+    s = random.uniform(1 - scale, 1 + scale)
+    # s = 2 ** random.uniform(-scale, scale)
+    R[:2] = cv2.getRotationMatrix2D(angle=a, center=(0, 0), scale=s)
+
+    # Shear
+    S = np.eye(3)
+    S[0, 1] = math.tan(
+        random.uniform(-shear, shear) * math.pi / 180
+    )  # x shear (deg)
+    S[1, 0] = math.tan(
+        random.uniform(-shear, shear) * math.pi / 180
+    )  # y shear (deg)
+
+    # Translation
+    T = np.eye(3)
+    T[0, 2] = (
+        random.uniform(0.5 - translate, 0.5 + translate) * width
+    )  # x translation (pixels)
+    T[1, 2] = (
+        random.uniform(0.5 - translate, 0.5 + translate) * height
+    )  # y translation (pixels)
+
+    # Combined rotation matrix
+    M = T @ S @ R @ P @ C  # order of operations (right to left) is IMPORTANT
+    if (
+        (border[0] != 0) or (border[1] != 0) or (M != np.eye(3)).any()
+    ):  # image changed
+        if perspective:
+            img = cv2.warpPerspective(
+                img, M, dsize=(width, height), borderValue=(114, 114, 114)
+            )
+        else:  # affine
+            img = cv2.warpAffine(
+                img, M[:2], dsize=(width, height), borderValue=(114, 114, 114)
+            )
+
+    # Transform label coordinates
+    n = len(targets)
+    if n:
+        new = np.zeros((n, 4))
+        xy = np.ones((n * 4, 3))
+        xy[:, :2] = targets[:, [1, 2, 3, 4, 1, 4, 3, 2]].reshape(
+            n * 4, 2
+        )  # x1y1, x2y2, x1y2, x2y1
+        xy = xy @ M.T  # transform
+        xy = (xy[:, :2] / xy[:, 2:3] if perspective else xy[:, :2]).reshape(
+            n, 8
+        )  # perspective rescale or affine
+
+        # create new boxes
+        x = xy[:, [0, 2, 4, 6]]
+        y = xy[:, [1, 3, 5, 7]]
+        new = (
+            np.concatenate((x.min(1), y.min(1), x.max(1), y.max(1)))
+            .reshape(4, n)
+            .T
+        )
+
+        # clip
+        new[:, [0, 2]] = new[:, [0, 2]].clip(0, width)
+        new[:, [1, 3]] = new[:, [1, 3]].clip(0, height)
+
+        # filter candidates
+        i = box_candidates(
+            box1=targets[:, 1:5].T * s, box2=new.T, area_thr=0.10
+        )
+        targets = targets[i]
+        targets[:, 1:5] = new[i]
+
+    return img, targets
diff --git a/train.py b/train.py
index 73208c55..1421a242 100755
--- a/train.py
+++ b/train.py
@@ -47,7 +47,8 @@
 
 torch.backends.cudnn.benchmark = True
 
-
+import cv2
+import numpy as np
 # The first arg parser parses out only the --config argument, this argument is used to
 # load a yaml file containing key-values that override the defaults for the main parser below
 config_parser = parser = argparse.ArgumentParser(description='Training Config', add_help=False)
@@ -149,6 +150,8 @@
                     help='Random erase count (default: 1)')
 parser.add_argument('--train-interpolation', type=str, default='random',
                     help='Training interpolation (random, bilinear, bicubic default: "random")')
+parser.add_argument('--mosaic', action='store_true', default=False,
+                    help='Mosaic Data Augmentation')
 
 # loss
 parser.add_argument('--smoothing', type=float, default=None, help='override model config label smoothing')
@@ -460,8 +463,7 @@ def create_datasets_and_loaders(
         Train loader, validation loader, evaluator
     """
     input_config = resolve_input_config(args, model_config=model_config)
-
-    dataset_train, dataset_eval = create_dataset(args.dataset, args.root)
+    dataset_train, dataset_eval = create_dataset(args.dataset, args.root, mosaic=args.mosaic)  
 
     # setup labeler in loader/collate_fn if not enabled in the model bench
     labeler = None