In 2007, Nixon was cast by Director Maria Aberg for the Royal Shakespeare Company in Roy Williams’ Days of Significance which played at the Swan Theatre in Stratford-Upon-Avon before moving to the Tricycle Theatre in London. The production was based on Much Ado About Nothing and was commissioned by the Royal Shakespeare Company.

In mid-2009 Nixon worked with Brooke Kinsella in S-27, and following that in 2010 with her very moving performance as Bea in the Soho Theatre production of the same title. Bea was written for her by the passionate and innovative Director and Playwright Mick Gordon after seeing her performance in S-27 the year before.

In 2011, Nixon played Dorathea in Shakespeare’s supposed lost play Cardenio (directed by RSC Artistic Director Gregory Doran). Charles Spencer commented in The Telegraph that "Lucy Briggs-Owen and Pippa Nixon give sharply defined neatly contrasting performances as the betrayed girls." In the same season Nixon played the prostitute, Shave'em, in Philip Massanger’s city comedy The City Madam, also at the Swan theatre.

In 2012, Nixon worked again with Maria Aberg in a production of Shakespeare's King John, where she played a female bastard alongside Alex Waldmann’s King John. The production which split the critics received a range of stars, and was well received by audiences.

Most recently Nixon played both Rosalind and Ophelia in the 2013 season. Here critics were impressed with Nixon’s portrayal of Shakespeare’s rejected and troubled heroine, Ophelia, in Hamlet. Michael Billington in The Guardian wrote, "Pippa Nixon's Ophelia is outstanding: a passionate schoolgirl fatally besotted by Hamlet." Fiona Mountford writing in The Evening Standard was particularly complementary about Nixon’s performance exclaiming, "Pippa Nixon makes a nicely vulnerable Ophelia, forced into renouncing her ardent love by misguided elders." Paul Taylor in The Independent praised Nixon’s approach to Ophelia declaring that ‘Nixon's Ophelia who, heart-rendingly, performs the mad scene in pristine white bridal dress and veil, is stunning". But it was Nixon’s captivating performance as Rosalind during the summer of 2013 in the joyous production of As You Like It, that was acclaimed by crics. Nixon was again reunited with Director Maria Aberg, and actor Alex Waldmann, a working relationship which hailed them as "the two most exciting actors in the company today". The portrayal of Rosalind received exceptional reviews.

In the Summer of 2014, Pippa could be seen on stage in the Theatre Royal Bath production of Helen Edmundson's adaptation of Emile Zola's novel Thérèse Raquin. Michael Billington wrote in his review that "Pippa Nixon is destined for stardom.". He went on to describe Nixon's "great gift is the ability to act with every inch of her body." The Daily Mail Review said, "Pippa Nixon’s performance as Therese is exhaustingly and enervatingly immersed in her character." Dominic Cavendish writing in The Telegraph said, "Rising star Pippa Nixon succeeds splendidly in suggesting Thérèse’s unbridled yearning with her bright, watchful eyes - an alluring force of suppressed nature in a voluminous turquoise dress." Paul Taylor in The Independent was equally positive about Pippa's performance and said "The glorious Pippa Nixon delivers a performance perfectly pitched to the production's propulsive, light-on-its-casters blend of the realist and the expressionist." The Observer review headline made the point that, "Pippa Nixon is a compelling presence."

In 2015, Nixon reprieved her role as Rosalind in BBC Radio 3's new production of Shakespeare's As You Like It. Orlando was played by Luke Norris who had played Olivier in the 2013 RSC stage version. Later in 2015, Nixon played Lotty in the BBC Radio 4 drama The Enchanted April.

In April 2016, Nixon starred in the Shakespeare Live event, which was screened on BBC 2 to celebrate Shakespeare 400. Here Nixon was reunited with her As You Like It co-star, Alex Waldmann. Together they performed a scene from As You Like It.

Pat Ashworth in The Stage wrote "Maria Aberg says she could not imagine directing this play with any Rosalind other than Pippa Nixon, whom she deems extraordinary. She is. She has a dancer’s body, a spareness and litheness which make her cocky and capering in the guise of a man and deeply vulnerable as a woman. But it’s her openness and quick-wittedness that is so appealing. She makes us able to read her mind, and that really is extraordinary." Lyn Gardner tweeted: ‘Pippa Nixon is enchanting, knee-trembling, sexy and sad in Maria Aberg’s As You Like It. Up there with the greatest Rosalinds’. Simon Tavener reviewing for What’sOnStage.com made the point that, "For my money, Pippa Nixon is the brightest star in the RSC ensemble at the moment and I hope that they continue to nurture and cherish her." Charles Spencer writing in The Telegraph felt that "Pippa Nixon now gives one of the most entrancing Rosalinds I have ever seen." Echoing Spencer, Michael Billington in his review of As You Like It in The Guardian went so far as to exclaim that, "Its chief delight is Pippa Nixon, who, for me, joins Vanessa Redgrave, Adrian Lester and the late Susan Fleetwood in the select pantheon of memorable Rosalinds ... It is a captivating, wittily androgynous performance that ushers Nixon to the threshold of stardom."