A slide rail assembly includes a first rail, a second rail and a slide assisting device. The first rail is arranged with an engaging part. The slide assisting device is movably mounted between the first rail and the second rail. The slide assisting device includes a main body, a plurality of slide assisting members and a fastening member. The plurality of slide assisting members are arranged on the main body and configured to contact the first rail and the second rail in a rolling manner. The fastening member is movably mounted to the main body. The second rail is movable relative to the first rail from a retracted position to an extension position along a direction. When the second rail is moved from the extension position along the direction, the slide assisting device is engaged with the engaging part of the first rail through the fastening member.