His first goal of 2011–12 came with the winner in Grimsby's 1–0 away win over Forest Green Rovers on 3 September 2011 after capitalising on a defensive mistake. Coulson was handed a one-match suspension after accumulating five yellow cards, missing the home match against Newport County on 19 November. He made an immediate return to the Grimsby line-up, starting in their 1–0 home win over League Two team Port Vale in the FA Cup first round on 22 November 2011.
In the 2011-12 season, Coulson scored his first goal of the year during Grimsby's away victory against Forest Green Rovers on September 3rd, 2011. He received a one-match suspension for accumulating five yellow cards and missed the home game against Newport County on November 19th. However, he returned to the starting lineup for Grimsby's FA Cup first round match against Port Vale on November 22nd, 2011.