Tamzin was born in 1970. She was brought up in Essex. Tamzin attended the Stagestruck Theatre Company as a young teenager as well as attending secondary school. At 16 she left school to join the London Studio Centre to study drama and dance. She left with that year's trophy for best all-rounder, which had previously been won by Liz Hurley.

Before television fame grabbed her in EastEnders, Tamzin had bit parts in The Bill and Men Behaving Badly.

Tamzin's many stage roles have included: Summer Holiday, Grease, Carousel, Oliver and Absent Friends. She says that Alan Aykbourn helped her acheive confidence in her performance, and encouraged her when it came to attending the audtion for the character of Melanie in Eastenders. Tamzin starred in Eastenders for four years before quitting to try other projects. She did not take any handcuff deals on her departure from Eastenders, preferring to stick with the option of picking and chosing her own roles.

Tamzin starred  in military drama series Red Cap (after a successful pilot at Christmas 2001) and has won acclaim for her role in the award-winning improvised drama Out of Control.

 Before she was famous: In 1987 Tamzin appeared as a presenter on the youth show No Limits (billed as 'Tammi Outhwaite').

Tamzin appeared in U2's music video for their song Mysterious Ways. She says that U2 are one of her favourite bands.