In January 2012, Kellett successfully earned a Professional Darts Corporation tour card on day two of the PDC's Pro Tour 'Q School' qualifying tournament. In June, he qualified for the European Tour Event 3 after defeating Nigel Heydon and William O'Connor in the UK qualifier. Kellett played Mervyn King in the first round in Düsseldorf and lost 3–6. He also reached the fourth European Tour Event and beat Colin Lloyd 6–4 in the first round in Stuttgart. Kellett faced Vincent van der Voort in the second round and lost 5–6. Kellett won the PDC World Championship qualifier in November, beating John Bowles 5–1 in the final, seeing off a total of seven players during the event to reach the World Championship for the first time. He lost to van der Voort in the first round, missing a total of 21 darts at a double, and was ranked world number 66 after the event.