Well, I have 27 monitors on it and it works quite well. Unfortunately I can't test it with a 34, but measured flat side by side it could work. The arms are too short at an angle, so it gets tight. But it depends a lot on the monitor and its edge. My 27s are borderless AOC 27" Q2790PQU/BT, 16:9, 2560x1440 (27", 2560x1440)