A door opening mechanism, in particular for public transport vehicles, the mechanism comprising: - a supporting structure; - a support member designed to carry a leaf of a door; - coupling means (13, 11, 22) that couple said support member to said supporting structure so that the support member is movable parallel to a horizontal plane, said plane being defined by a first and by a second axis (X, Z) orthogonal to one another; - a guide fixed with respect to said supporting structure, slidingly engaged by said support member and shaped so as to guide said support member along a trajectory on said horizontal plane to open/close said leaf; - a slider designed to be actuated by an actuator assembly so as to translate with respect to said supporting structure along said first axis between a first end-of-stroke position, corresponding to a closed leaf condition, and a second end-of-stroke position, corresponding to an open leaf condition; and - transmission means (36; 36') that couple said slider to said support member so that a translation of said slider corresponds to a movement of said support member along said trajectory; said transmission means (36; 36') comprising a first cam (37; 37') carried by a first element defined by one of either said support member and said slider, and a first follower (46; 46') engaging said first cam (37; 37') and carried by a second element defined by the other of either said support member and said slider; characterised in that said first cam (37; 37') is shaped to prevent said slider from translating towards the second end-of-stroke position, when said slider is arranged in the first end-of-stroke position and said support member receives a force directed parallel to said second axis, wherein said first cam (37; 37') defines a curvilinear path to be followed by said first follower (46; 46') and comprising two extreme points (E, F) and an intermediate point between said extreme points (E, F) defining a dead point position for the first follower (46; 46'); the intermediate point coinciding with the apex of an elbow-shaped section of said curvilinear path or belonging to a straight section of said curvilinear path parallel to said first axis. - a supporting structure; - a support member designed to carry a leaf of a door; - coupling means (13, 11, 22) that couple said support member to said supporting structure so that the support member is movable parallel to a horizontal plane, said plane being defined by a first and by a second axis (X, Z) orthogonal to one another; - a guide fixed with respect to said supporting structure, slidingly engaged by said support member and shaped so as to guide said support member along a trajectory on said horizontal plane to open/close said leaf; - a slider designed to be actuated by an actuator assembly so as to translate with respect to said supporting structure along said first axis between a first end-of-stroke position, corresponding to a closed leaf condition, and a second end-of-stroke position, corresponding to an open leaf condition; and - transmission means (36; 36') that couple said slider to said support member so that a translation of said slider corresponds to a movement of said support member along said trajectory;