We live in a 3D world, and our brain uses binocular disparity to extract depth information from the 2D retinal images in stereopsis.Such disparity cue, however, may fail to reach awareness if we have an inherent assumption about an objects depth property.Here we report a new case of depth illusion in biological motion perception and further investigate the neural fate of such invisible stereoscopic cues.In a subgroup of observers with normal stereopsis, we found that they could not discern between 3D point-light walkers with unambiguous but opposite disparity cues (i.e., walking towards vs.walking away).Instead, they interpreted all of the 3D walkers as walking towards the viewer due to a robust perceptual bias linked with biological motion perception.Surprisingly, in a series of depth-irrelevant tasks, these observers demonstrated significant perceptual asymmetry between the point-light walkers with opposite walking directions as if they could "see" such subliminal disparity cues.Our findings provide compelling evidence that the unconscious stereoscopic cues modulate the conscious perception of biological motion and shed new light on the neural encoding of binocular disparity in the human visual system.