We propose a generic framework MEDUSA (Multimodal Estimated-Depth Unification with Self-Attention) to fuse RGB and depth information using multimodal transformers in the context of object detection. Unlike previous methods that use the depth measured from various physical sensors such as Kinect and Lidar, we show that the depth maps inferred by a monocular depth estimator can play an important role to enhance the performance of modern object detectors. In order to make use of the estimated depth, MEDUSA encompasses a robust feature extraction phase, followed by multimodal
transformers for RGB-D fusion. The main strength of MEDUSA lies in its broad applicability for any existing large-scale RGB datasets including PASCAL VOC and Microsoft COCO. Extensive experiments with three datasets show that MEDUSA achieves higher precision than several strong baselines.