On 17 September 2011 he was sent off against Rangers for a second bookable offence, a challenge on Steven Davis. Mulgrew scored his first SPL goal for Celtic on 15 October 2011, a headed equaliser at Rugby Park as Celtic came back from 3–0 down to draw 3–3 with Kilmarnock. On 7 April 2012, Celtic beat Kilmarnock at Rugby Park to confirm them as Scottish Premier League champions. Mulgrew scored two and set up two in the 6–0 win. On 29 April 2012, he scored Celtic's first goal in a 3–0 victory over Rangers. His performances won him the SPL, Players' and writers' player of the year awards for 2011–12. He also picked up Celtic's Player of the Year and Player's Player of the Year awards.