A livestock head holder features a top holding member, a bottom holding member and an intermediate link connecting same. An operating lever connected to the bottom holding member so that downward pulling of the operating lever performs a closing stroke of the head holder that swings both holding members into place against the animal's neck. A lock and release mechanism automatically blocks the linkage from performing a reverse opening stroke that withdraws the holding members away from one another under raising of the operating lever. The operating lever is arranged to release the locking action during initial raising of lever to enable completion of the opening stroke, thereby using the same lever for all opening, closing and unlocking functions, whereas prior designs required a separate lock- release mechanism.