After a disappointing start to the 2008–09 season, Robertson reached the final of the 2008 Bahrain Championship, where he played Matthew Stevens. The match lasted almost six hours in total, with the Australian edging it 9–7. During the 2009 Masters, Robertson and opponent Stephen Maguire set a record of five consecutive century breaks. Robertson made two centuries, and Maguire made three, with his third sealing a 6–3 win over the Australian. At the 2009 World Championship, Robertson defeated Steve Davis, Ali Carter and Stephen Maguire to reach the semi-finals of the World Championship for the first time, before losing to Shaun Murphy 14–17 (after at one stage recovering from 7–14 behind to level at 14–14).