The Underworld: Rise of the Lycans star will play Captain Rachel Dalton, according to Deadline.
After a long stint in North Africa, Dalton will take over as the new head of British military unit Section 20, following the demise of Colonel Eleanor Grant (Amanda Mealing).
Mitra previously starred in ABC's Boston Legal and played a recurring role on FX drama Nip/Tuck.
She has also appeared on Stargate Universe and The Gates, while her film credits include 2007's The Number 23 opposite Jim Carrey and 2008's Doomsday.
Sky and Cinemax/HBO confirmed that Strike Back would return for ten more episodes in October. Series leads Philip Winchester (Michael Stonebridge) and Sullivan Stapleton (Damian Scott) are expected to reprise their roles.
Filming on the new season is scheduled to begin shortly in South Africa.
> Strike Back exec working on new Cinemax drama
Watch the stars of Strike Back discuss the show with Digital Spy below: