A display support device includes a hollow hanging arm having a movable end portion, and a pressure cylinder movably disposed in the hanging arm and including a fixed rod that extends through a cylinder body thereof and that has an open end, and a control pin extending through the open end and having an end surface. A control unit is operable to control the control pin between a locking position, in which the end surface is flush with the open end and the cylinder body is immovable relative to the fixed rod, and an unlocking position, in which the end surface is spaced apart from the open end and the cylinder body is movable relative to the fixed rod. A carrier unit is pivotally connected to the movable end portion.