In 1981, Brightman auditioned for composer Andrew Lloyd Webber’s new West End musical Cats, successfully landing the role of Jemima. The audition marked the beginning of both her professional and personal association with Webber. She went on to appear in notable productions including The Pirates of Penzance and Masquerade, and starred in the title role of the children's opera Nightingale. Her performance caught Webber's attention, and after a developing romance, they married in 1984.

Brightman played significant roles in many of Webber’s major productions, including The Phantom of the Opera, Song and Dance, and Requiem. Notably, the lead role of Christine Daaé in Phantom was created specifically for her. The production enjoyed immense commercial success, breaking box office records with $18 million in advance sales and becoming one of Broadway’s most lucrative musicals. Despite the commercial success, American critics were less enthusiastic, offering lukewarm reviews of Brightman’s performance.

Transition to Studio Recording

Following her Broadway success, Brightman performed internationally in Andrew Lloyd Webber's compositions and began to focus more on studio work. She released two albums during this transitional period: 1988’s The Trees They Grow So High and 1989’s The Songs That Got Away. Her shift to a recording career coincided with growing tensions in her marriage. In 1990, she and Webber separated and subsequently divorced.

Classical Crossover Success

After stepping away from stage performances, Brightman partnered with Frank Peterson, formerly of the German band Enigma, to explore a new musical direction—classical crossover. The genre, which blends classical elements with pop music, became a defining feature of Brightman's post-theater career. Their first album together, 1993's Dive, earned Brightman her first Gold record in Canada. The follow-up, 1995's Fly, furthered her success in Europe, with the hit single "A Question of Honour" debuting during a World Boxing Championship in Germany and quickly gaining traction.

1997’s Timeless (released as Time to Say Goodbye in the United States) became her most critically and commercially successful album. The duet "Time to Say Goodbye" with Italian tenor Andrea Bocelli was a global sensation, selling over 14 million copies worldwide and going multiplatinum in several countries, including more than 3 million copies sold in Germany alone. The record established Brightman as a major figure in the classical crossover genre and greatly expanded her international audience.