A slide rail assembly includes a first rail, a second rail, a blocking member, a positioning member, and an operating member, configured to operate one of the blocking member and the positioning member. The first rail includes a positioning feature; the second rail is movable relative to the first rail. The blocking member and the positioning member are movably mounted on the second rail, and are respectively at one of the first state and the second state. When the second rail is moved in an extending direction from a retracted position to an extending position relative to the first rail, the second rail is prevented from being moved in the extending direction or a retracting direction from the second extending position relatively to the first rail, through the positioning member and the blocking member respectively corresponding to two portions of the positioning feature of the first rail.