A pet collar assembly is removably attached to a pet collar and carries a leash. The assembly allows for extending and retracting the leash and includes a housing, an actuator assembly for actuating retraction of the leash upon receiving force higher than a threshold retraction force, and a spool communicating with the actuator assembly and biased for coiling the leash. The actuator assembly has a button and a button shaft that mechanically communicates with a hook shaft attached to a hook. The hook engages a plurality of teeth disposed on the circumference of a rim of the spool. An elastic band applies force against the hook so that the actuator assembly remains in a locked configuration unless a force higher than the threshold retraction force is received by the button.