A slide rail assembly, comprising: a first rail; a second rail movable relative to the first rail between a first position and a second position; a third rail movable relative to the second rail; a supporting member; wherein: a locking mechanism comprising a locking member movably mounted to the second rail, wherein the locking member has a first part partially extending out of a first side of the second rail, and a second part partially extending out of a second side of the second rail, wherein a pivoting member arranged between the first part and second part is configured to pivot the locking member to the second rail, such that the locking member of the locking mechanism is configured to be in a first state or a second state, wherein when the locking mechanism is in the first state, the locking mechanism is configured to prevent the second rail from being moved relative to the first rail from the second position toward the first position; and an operating member having an elongated hole, wherein the supporting member passes through a portion of the elongated hole for mounting the operating member to the second rail, such that the operating member is configured to be manually operated to switch the locking mechanism from the first state to the second state, in order to allow the second rail to be movable relative to the first rail from the second position toward the first position; wherein the second rail has a first side and a second side opposite to the first side, the operating member is located at the first side of the second rail, the second rail further has an extension hole; the slide rail assembly being characterized by the operating member comprising an auxiliary feature passing through the extension hole and located at the second side of the second rail, the auxiliary feature being configured to drive the locking mechanism to switch from the first state to the second state in response to the operating member being manually operated. a first rail; a second rail movable relative to the first rail between a first position and a second position; a third rail movable relative to the second rail; a supporting member; wherein: a locking mechanism comprising a locking member movably mounted to the second rail, wherein the locking member has a first part partially extending out of a first side of the second rail, and a second part partially extending out of a second side of the second rail, wherein a pivoting member arranged between the first part and second part is configured to pivot the locking member to the second rail, such that the locking member of the locking mechanism is configured to be in a first state or a second state, wherein when the locking mechanism is in the first state, the locking mechanism is configured to prevent the second rail from being moved relative to the first rail from the second position toward the first position; and an operating member having an elongated hole, wherein the supporting member passes through a portion of the elongated hole for mounting the operating member to the second rail, such that the operating member is configured to be manually operated to switch the locking mechanism from the first state to the second state, in order to allow the second rail to be movable relative to the first rail from the second position toward the first position; wherein the second rail has a first side and a second side opposite to the first side, the operating member is located at the first side of the second rail, the second rail further has an extension hole; the slide rail assembly being characterized by the operating member comprising an auxiliary feature passing through the extension hole and located at the second side of the second rail, the auxiliary feature being configured to drive the locking mechanism to switch from the first state to the second state in response to the operating member being manually operated. a locking mechanism comprising a locking member movably mounted to the second rail, wherein the locking member has a first part partially extending out of a first side of the second rail, and a second part partially extending out of a second side of the second rail, wherein a pivoting member arranged between the first part and second part is configured to pivot the locking member to the second rail, such that the locking member of the locking mechanism is configured to be in a first state or a second state, wherein when the locking mechanism is in the first state, the locking mechanism is configured to prevent the second rail from being moved relative to the first rail from the second position toward the first position; and an operating member having an elongated hole, wherein the supporting member passes through a portion of the elongated hole for mounting the operating member to the second rail, such that the operating member is configured to be manually operated to switch the locking mechanism from the first state to the second state, in order to allow the second rail to be movable relative to the first rail from the second position toward the first position; wherein the second rail has a first side and a second side opposite to the first side, the operating member is located at the first side of the second rail, the second rail further has an extension hole; the slide rail assembly being characterized by the operating member comprising an auxiliary feature passing through the extension hole and located at the second side of the second rail, the auxiliary feature being configured to drive the locking mechanism to switch from the first state to the second state in response to the operating member being manually operated.