Cousins is a product of the Colchester United Academy, he had work experience loan spells with Whitton United, Staines Town, Enfield Town and Yeading. Cousins got his first taste of first-team action with Colchester in the 2007–08 season. On 27 May 2011, Cousins agreed a new two-year deal with the club and was given the number 1 shirt ahead of the 2012–13 season. He made his first appearance in the number 1 shirt on 14 August 2012. In June 2014, he signed for Dagenham & Redbridge on a two-year deal and at the end of the season was named runner up in player of the year awards. In June 2016 Cousins signed a new contract after the club was relegated to the National League. Cousins joined Barnet on a two-year deal in June 2018, where he played 53 games, keeping 20 clean sheets. On 3 June 2019, Cousins joined Bromley for an undisclosed fee. On 24 June 2022, Cousins signed for National League South club Ebbsfleet United.