[7] After the Arts Council of Great Britain was split in 1994, at age 34 Scanlan decided to try becoming a professional actor, quickly gaining the role as a nurse in ITV1's Peak Practice.

[8] Scanlan is known for her portrayal of Terri Coverley, the notoriously useless senior press officer for the Department of Social Affairs and Citizenship in the British comedy television series The Thick of It from 2005 to 2012.

The comedy series was adapted for an American audience with HBO, with Scanlan on board as an executive producer to closely work on script development.

Scanlan and Vicki Pepperdine teamed up again to write and star in their BBC Four comedy series Puppy Love, which follows two women at their dog training classes on the Wirral.

Scanlan plays lead character DI Inspector 'Viv Deering' in Paul Abbott's BAFTA nominated and RTS award-winning primetime drama, No Offence.

Additional television credits include Death Comes To Pemberley, Fungus the Bogeyman, Mapp & Lucia, Heading Out, Stella, Doc Martin, One Foot in the Grave and Spaced.

On stage, Scanlan has worked with Thea Sharrock in her production of Cloud 9 at the Almeida Theatre and Top Girls, with Rufus Norris in Vernon God Little at the Young Vic, and featured in Polly Teale's Madame Bovery.