 On 19 November 2009, Coulson signed for League Two side Grimsby Town on an initial one-month loan. He made his debut two days later after starting in a 0 – 0 draw at Lincoln City. He scored his first goal for Grimsby on 5 December 2009 in his fourth appearance, a 1 – 1 draw with Dagenham & Redbridge, opening the scoring in the 36th minute before Dagenham equalised in the second half. His loan was extended for a second month in December 2009, keeping him at Grimsby until 23 January 2010. Shortly before the loan was due to expire, Coulson's stay at Grimsby was extended until the end of 2009 – 10 on 19 January 2010. He finished the season with five goals in 29 appearances for Grimsby, with the side being relegated to the Conference Premier.
