A slide rail assembly includes a first rail, a second rail and a locking device. The first rail includes a blocking part. The second rail is movable relative to the first rail. The locking device is arranged on the second rail. The locking device includes a first part and a second part. A first space is defined between the first part and the second part. When the second rail is located at a predetermined position relative to the first rail, a second space is defined between the first part and the second part and configured to accommodate the blocking part, and the first part and the second part of the locking device are configured to respectively block two sides of the blocking part of the first rail.