When she attended Red Deer College, Lang became drawn to country music. . Soon, she became fascinated with the life and music of Patsy Cline and ultimately determined to pursue a career as a professional singer. Lang formed a Patsy Cline tribute band called the Reclines in 1983, and they recorded a debut album, Friday Dance Promenade. Also in 1983, she presented a performance art piece, a seven-hour re-enactment of the transplantation of an artificial heart for Barney Clark, a retired American dentist. A Truly Western Experience was released in 1984 and received strong reviews and led to national attention in Canada.
Singing at country and western venues in Canada, Lang made several recordings that received good reviews and earned a 1985 Juno Award for Most Promising Female Vocalist. She accepted the award wearing a wedding dress and made numerous tongue-in-cheek promises about what she would and would not do in the future, thus fulfilling the title of "Most Promising." She has won eight Juno Awards.
The year 1988 marked the release of Shadowland, an album of torch country produced by the legendary Owen Bradley. That year she performed "Turn Me Round" at the closing ceremonies of the XV Winter Olympics in Calgary, Alberta. Later that same year she would sing background vocals with Jennifer Warnes and Bonnie Raitt for Orbison's acclaimed television special, Roy Orbison and Friends, A Black and White Night. Lang also guest-starred on Pee-wee's Playhouse Christmas Special in 1988, where she sang "Jingle Bell Rock".
The 1992 album, Ingénue, a set of adult contemporary pop songs that showed comparatively little country influence, contained her most popular song, "Constant Craving." That song brought her multi-million sales, much critical acclaim, and the Grammy Award for Best Female Pop Vocal Performance. Another top ten single from the record was "Miss Chatelaine". The salsa-inspired track was ironic; Chatelaine is a Canadian women's magazine which once chose Lang as its "Woman of the Year," and the song's video depicted Lang in an exaggeratedly feminine manner, surrounded by bright pastel colours and a profusion of bubbles reminiscent of a performance on the Lawrence Welk show.
Lang contributed much of the music towards Gus Van Sant's soundtrack of the film Even Cowgirls Get the Blues, and also did a cover of "Skylark" for the 1997 film adaptation of Midnight in the Garden of Good and Evil. She performed "Surrender" for the closing titles of the James Bond film Tomorrow Never Dies, having previously worked with Bond composer David Arnold on his album, Shaken and Stirred: The David Arnold James Bond Project.
In 1996, she was made an Officer of the Order of Canada.
In 1997, Drag, an album of cover tunes dedicated to 'smoke' (specifically cigarette smoking) was released, although the album cover and booklet photographs show Lang in a men's suit, referring to crossdressing as another possible meaning of the word 'drag'. The songs on Drag include "Smoke Dreams," from the '40s, Steve Miller Band's "The Joker," "Smoke Rings," the theme from the cult movie Valley of the Dolls, and 8 other smoke-themed songs.
Lang ranked #33 on VH-1's 100 Greatest Women in Rock & Roll in 1999 and #26 on CMT' 40 Greatest Women in Country Music in 2002, one of only eight women to make both lists. The others were Linda Ronstadt, Patsy Cline, Dolly Parton, Tammy Wynette, Loretta Lynn, Lucinda Williams and Emmylou Harris.
On subsequent tours, critical acclaim continued to come her way. In 2004, Stephen Holden of The New York Times wrote: "Few singers command such perfection of pitch. Her voice, at once beautiful and unadorned and softened with a veil of smoke, invariably hits the middle of a note and remains there. She discreetly flaunted her technique, drawing out notes and shading them from sustained cries into softer, vibrato-laden murmurs. She balanced her commitment to the material with humor, projecting a twinkling merriment behind it all.
In the same year, she released Hymns of the 49th Parallel, which featured cover versions of songs by iconic English-speaking Canadian singer-songwriters: Bruce Cockburn, Leonard Cohen, Joni Mitchell, Ron Sexsmith, Jane Siberry, and Neil Young. According to the Canadian Record Industry Association (CRIA), in April 2006 the album went platinum in Canada selling over 100,000 copies. In December 2007 the album reached double platinum status in Australia selling over 140,000 copies.
In 2006, Lang paired with singer Madeleine Peyroux on a cover of the Joni Mitchell song "River" for Peyroux's album, Half the Perfect World. That same year Lang was featured in Nellie McKay's second album, Pretty Little Head, singing with McKay in "We Had it Right". That same year, Lang sang a version of The Beatles' "Golden Slumbers" for the Happy Feet film soundtrack.
In 2007, she partnered with Anne Murray on a re-make of Murray's hit "A Love Song," to be featured on Murray's CD, Anne Murray Duets: Friends and Legends. The duet was recorded in Los Angeles, and on Murray's official website there is a picture of Murray and Lang kneeling behind Murray's star on the Hollywood Walk of Fame. Anne Murray was one of Lang's childhood idols.
Lang appeared on the cover of the August 1993 issue of Vanity Fair. The cover featured Lang in a barber chair while model Cindy Crawford appeared to shave her face with a straight razor. The issue contained a detailed article about Lang which observed that she had thought that she would be ostracized by the country-music industry when she came out as a lesbian; but Nashville was accepting, and her records continued to sell. When she appeared in an ad for PETA however, Nashville was less impressed owing to the relationship between country music and cattle ranching.
Lang collaborated with Annie Lennox in the production of the charity record Sing released on December 1, 2007 (World AIDS Day), to raise awareness of the transmission of HIV to unborn children in Africa.
In April 2008, Lang spent time in Melbourne, Australia, as a guest editorialist for The Age. This was in connection with her support for the Tibet human rights issues. On April 24, 2008, she joined pro-Tibet protesters in Canberra as the Beijing 2008 Olympic torch relay made its way through the Australian capital.