Several clubs including Liverpool and Fulham showed interest in signing Watt during the 2011 January transfer window. After a trial with Rangers and a week’s training with Liverpool, Watt was signed by his boyhood heroes Celtic on 4 January, for a reported fee of £80,000 and future payments dependent on his first-team progression. He signed a three-year contract.
Watt made his Celtic debut on 22 April 2012 in a 3–0 win over Motherwell. He scored two goals within five minutes of coming on as a substitute.
On 25 August 2012, Watt made his first start for Celtic scoring two goals in their 4–2 away win against Inverness. He made his Champions League debut on 7 November 2012, coming on as a second-half substitute for Mikael Lustig and scoring in the 83rd minute in a 2–1 home win against Barcelona. Four days later, he came off the subs bench to score again, this time in a 1–1 draw against St Johnstone in the league. On 15 November 2012, Watt signed a new contract extending his stay with Celtic until 2016. Watt made a further 14 appearances for Celtic that season, mostly coming on as a substitute, and did not score any more goals. He did however win his first major honour as Celtic won their 44th league championship title in May 2013; his 20 league appearances over the season entitling him to a league winner’s medal.
