Before she turned twenty, Nagra left Leicester for London, forgoing university to pursue a theatrical career and her childhood dreams of becoming an actress. After selling her prized viola, she found herself living alone in Peckham, south London, employed in a stocktaking job and struggling to find theatrical work.

Nagra's first London theatrical job came in 1994[citation needed] when she was cast as the Princess in Sleeping Beauty, a Christmas-time pantomime production at the Theatre Royal Stratford East. Although most critics seemed rather unimpressed with the show, Nagra's performance is notable in that she was a woman of colour portraying a traditionally white character.

After Sleeping Beauty, Nagra worked with small Indian theatre companies such as Tara Arts and Tamasha. The roles marked the first of many early career opportunities in theatre that led eventually to the radio and television appearances that also defined her career throughout most of the 1990s.

In 1996, Nagra took a small part in Fair Ladies at a Game of Poem Cards, written by Chikamatsu Monzaemon and performed at Cottesloe, Royal National Theatre. It was there that she met Irish actor Kieran Creggan, with whom she later moved into a flat in Kennington, south London. Their relationship continued for five years.

Although lacking formal theatrical training, Nagra signed with veteran London-based agent Joan Brown, after which she began to land her first television roles — a bit part on the British medical drama Casualty, where she played a girl attacked with a broken bottle, and a small role in the television movie King Girl in which Nagra portrayed an abusive member of a girls' gang.

In 1997, Nagra appeared in the three-part drama Turning World, starring Roshan Seth. The following year she appeared on Casualty for the second time.

The year 1999 saw her playing the part of a convenience store clerk in the television movie Donovan Quick, starring Colin Firth. Also of note are appearances on the British comedy shows Goodness Gracious Me and The Kumars at No. 42.

While slowly building a reputation on British television, Nagra also dabbled in radio, with parts in, among others, radio plays written by noted author and playwright Tanika Gupta. In 1998, Nagra was part of Dancing Girls of Lahore, a radio play co-written by her future Bend It Like Beckham co-star, Shaheen Khan. In 2001, Nagra provided the voice of a Muslim girl in Arena: The Veil, a docu-drama about women who choose to wear the Muslim head scarf.

Although Nagra had cut her teeth in television and, to a lesser extent, in radio, her stage performances are perhaps the most noteworthy element in her corpus of work during her London years. Not long after Fair Ladies at a Game of Poem Cards, Nagra was cast in 1997's Oh Sweet Sita, an adaptation of Indian mythology about Rama and his dutiful wife Sita.

Starring in the title role of Sita, Nagra caught the attention of director Gurinder Chadha, who would later write the script for Bend It Like Beckham with Nagra in mind for the lead role. Although Chadha was charmed by Nagra[citation needed], it would be five more years before the spectacular results of their collaboration would materialize.

Although she was fast becoming a star on the stages of London, it was 2002's surprise blockbuster Bend It Like Beckham, Nagra's first film, that turned her into an international celebrity almost overnight.