A retractable animal leash assembly including a housing suitable for being held in one hand is disclosed, with a freely moveable, but, if desired, lockable leash being arranged partially coiled within the housing, this housing mounting a brake key operable by the holding hand for momentarily blocking the portion of the leash located outside the holding at a desired length with a brake lock mechanism for holding the brake key in the locking position. This brake lock mechanism comprises a two-armed lever arranged to be moved between two positions on the housing reachable by the same finger/thumb of the holding hand, the handling of this pivoted lever occurring in an ergonomically optimal manner.