At the 2019 World Championship, Cahill was given a qualifying wildcard spot by the World Professional Billiards and Snooker Association, despite being an amateur. He played Andrew Higginson in the first round of qualifying, and led 7–0 and 8–2, before Higginson won 7 straight frames to lead 9–8. Cahill won the last two frames of the match to win 10–9 and progress to the second round of qualifying. He then defeated Michael Holt 10–7, to set up a final qualifying round match against fellow amateur player Michael Judge. Cahill defeated Judge 10–6 to become the first amateur player to play at the main stages of the world championships at the Crucible Theatre.