Petersen retained the South African Open in 2011 to qualify for the 2012 PDC World Darts Championship, where he edged out José Oliveira de Sousa 4–3 (legs) in the preliminary round to reach the last 64 for the second successive year. Petersen played Steve Brown in the first round and recovered from 2–1 down in sets to win 3–2, also recovering from 2–0 down in legs in the deciding set and surviving one match dart. Petersen said after the win that it was a "dream come true" and that he was sure he had more in him. He played Gary Anderson in the second round and played the best he has in front of the television cameras. However, the class of his opponent came through and he lost 4–2, with Anderson stating after the match that "Devon became very tough for me". Petersen himself said that he would "work hard and come back a better player".