Bennett-Warner graduated from RADA in 2010, but left early to take on the role of Sophie in Lynn Nottage's Ruined at the Almeida Theatre. Before completing the course she was awarded the prestigious Carleton Hobbs Radio Award. However, due to another job commitment she was unable to join the radio rep.[clarification needed]
Bennett-Warner received an Ian Charleson commendation for King Lear. She then took the role of Denise in D. C. Moore's new play The Swan — in a role that had been written for her – at the National Theatre[5] followed by playing Queen Isabel in Michael Grandage's swan song Richard II at the Donmar Warehouse with Eddie Redmayne in the title role and Andrew Buchan as Bolingbroke in 2010.[6] She received positive reviews from the critics, with Kate Bassett from The Independent saying: "Both of them (Redmayne and Buchan) are, in fact, outshone by Pippa Bennett-Warner in the cameo role of Isabel, Richard’s devoted, fiery queen."[7]
In 2012, she played the lead role in Vivienne Franzmann's second play The Witness, at the Royal Court Theatre.[4] She received rave reviews with Susannah Clapp from The Observer stating, "Always thought Pippa Bennett-Warner had big future. Now she is having it in 'The Witness' at Royal Court...There are actresses (even actors) who are more flashy, who more obviously inflect every detail of a speech. PBW is completely natural. Audiences of course admire her: but they do something else, which is not always the same thing: they believe her". Bennett-Warner went on to secure a nomination for Best Actress at the Evening Standard Theatre Awards 2012, alongside Cate Blanchett and Dame Eileen Atkins and was named as one of the 1,000 Most Influential Londoners in 2012 in the category "Generation Next" by The Evening Standard.
Bennett-Warner is good friends with Jonathan Bailey who she appeared with in Doctor Who's "Time Heist" episode in 2014.[9] Bailey also photographed her for a profile for Rose & Ivy magazine in 2021.[10]