He is best known for playing Neil Sutherland in the BAFTA-winning E4 comedy The Inbetweeners and more recently as 'Medium' Dan, in the ITV sitcom Kate & Koji.

[5] Harrison also starred in all three seasons of The Increasingly Poor Decisions of Todd Margaret, created by David Cross.

[citation needed] His film work includes Keeping Rosy with Maxine Peake, Madness in the Method and Re-Uniting the Rubins with Timothy Spall; he also starred in Her Eyes Met With Mine, a short film by Slightly Ajar Productions.

[5] In 2018, he directed the award-winning short film Hooves of Clay, in which he also starred alongside Rebecca Humphries.

[11] In 2018, Harrison scored the winning penalty goal in the charitable event Soccer Aid.