A stent delivery device having a locking mechanism. The device includes a handle assembly, an elongate inner member, and an elongate outer tubular member surrounding the elongate inner member. The handle assembly includes a handle attached to one of the inner member and the outer tubular member, and an actuator attached to the other of the inner member and the outer tubular member. Actuation of the actuator relative to the handle between a first position and a second position causes axial movement of the outer tubular member relative to the inner member. The locking mechanism has a locked position in which the actuator is prevented from moving from the first position to the second position and an unlocked position in which the actuator is permitted to move from the first position to the second position.