Despite his ranking, he chose not to accept an invitation to play in the 2020 Masters invitational event. O'Sullivan's first performance in 2020 was the World Grand Prix, where he was beaten 3–5 by Graeme Dott. He then reached the semi-finals of the 2020 Welsh Open in which he lost 5–6 to Kyren Wilson. He also played at the 2020 Snooker Shoot Out where he lost in the second round to Billy Castle. Due to a lack of earnings in ranking tournaments over the course of the season, he was unable to defend the Players Championship, as he was pipped to the last remaining place by the two finalists of the Shoot Out.