An automatic mooring device for vessels includes a coupling element associable with a mooring point or with a vessel, and a capture element, associable with a vessel or with a mooring point and detachably engageable with the coupling element. The coupling element includes an autonomous floating body; a supporting element fixed to the floating body; a hook element associated with the supporting element and movable with respect to the supporting element from a coupling position to a release position; a safety lever, which can engage the hook element so as to close its bend for the retention of the capture element; and elements for retaining the hook element in the coupling position.