At the Masters in January, O'Sullivan went out 4–6 in the first round against Mark Allen. O'Sullivan reached the semi-finals in the Snooker Shoot-Out in January 2011, before losing against Robert Milkins. He made the two highest breaks of the tournament, 112 and 123. He then lost in the first round of the next two ranking tournaments, both times against Ryan Day. He lost 2–4 at the Welsh Open, and 2–5 at the China Open. He reached the quarter-finals of the World Championship by defeating Dominic Dale 10–2 in the first round and Shaun Murphy 13–10 in the second round, but lost 10–13 against eventual winner John Higgins.