A slide rail assembly is provided and includes a first rail, a second rail movable with respect to the first rail, a working member, an operating member and a blocking member. When the second rail is located at an extended position with respect to the first rail and the working member is in a first state, the working member and a blocking feature of the first rail block each other for restraining the second rail from moving toward a first predetermined direction from the extended position. The blocking member is switchable between a blocking state and a non-blocking state for restraining the operating member from driving the working member to disengage from the first state or for allowing the operating member to drive the working member from the first state to a second state. Besides, a related slide rail kit is also provided.