Lee began the 2011–12 season ranked 18 and lost in qualifying for the Australian Goldfields Open and in the first round of the Shanghai Masters. However, he had an excellent run of form in the PTC Events by reaching the quarter-finals of Events 3 and 4 and going one better in Event 6, as he lost to Neil Robertson in the last 4. This meant that Lee returned to the top 16 in October, as he was ranked 13 and therefore gained automatic entry into the upcoming ranking events. He lost in the first round of the 2011 UK Championship and in the German Masters reached his first semi-final since the 2006 Northern Ireland Trophy, but could not get past Ronnie O'Sullivan, who won 6–4. He then made it to the quarter-finals of the Welsh Open, where he was put off by a mobile phone ringing on his back-swing in a deciding frame against Ding Junhui and went on to lose the match. He used his frustration from the incident to good effect however, as he beat Dominic Dale, Neil Robertson, Graeme Dott and Robert Milkins to reach the final of the World Open, his first since the 2006 Welsh Open. He played Mark Allen, but was dominated throughout, as he lost the match 1–10.