Growing up in a musical family, Eva Cassidy began singing at age nine. Her father played acoustic bass, her brother fiddle. She sang with couple rock bands in high school, and did a little country singing one early summer. Eventually, a friend brought her to Chris Biondo's studio and Biondo was blown away by her forceful voice. He encouraged her and helped her find work as a backup singer for various acts. In 1990 Biondo convinced Cassidy to form the 5-piece "Eva Cassidy Band" and she began to perform in the Washington D.C. area.

Cassidy also performed backing vocals on D.C. go-go funksters E.U.'s Livin' Large album (singing all of her own harmony parts to give the illusion of a choir) and, later, on gangsta rapper E-40's "I Wanna Thank You."

In 1991 Biondo played a tape of Eva to Chuck Brown, best known as a "Go-Go" singer, although he is also an accomplished jazz and blues vocalist. This led to the first commercial recording of Cassidy, the duet album The Other Side, which featured performances of classic songs such as "Fever", Billie Holliday's "God Bless the Child" and Eva's signature tune "Somewhere Over the Rainbow". In 1993 the two began performing around the D.C. area together; helped by Brown's outgoing showmanship, Cassidy finally began to lose some of the insecurity and intense fear that usually kept her away from live performance. Several record labels showed interest in signing Cassidy, but her recordings were too eclectic, covering folk, jazz, blues, gospel, R&B, and pop/rock. Unable to categorize her, she remained unsigned.

In September 1993, Eva Cassidy had a malignant mole removed from below her neck. It was a harbinger of things to come. In early 1994, Blue Note showed some interest in teaming Cassidy with a jazz-pop outfit from Philadelphia called Pieces of a Dream. They recorded the single "Goodbye Manhattan" together, and Cassidy toured with them, but didn't really care for their style and returned to D.C., playing more gigs on her own At the end of the year, she won a local music award for traditional jazz vocals.

Unable to secure a record deal, Biondo and Cassidy's manager decided to record an album themselves. In January 1996, Cassidy did two performances at the D.C. club Blues Alley, and despite her dissatisfaction with the quality of her performance, the album Live at Blues Alley was compiled from the recordings and released that year to much acclaim in the D.C. area. It would be the only solo album to appear during Cassidy's lifetime.

Painting murals at elementary schools during the summer of 1996, and began experiencing problems with her hip. Cassidy assumed was related to her frequent use of stepladders at work. Tests revealed that her hip was broken, and further tests revealed the melanoma from several years before had spread to her lungs and bones. Cassidy started chemotherapy, but it was too late. She died of melanoma in November of 1996 at the age of 33, leaving behind a scant few recordings.

D.C.-based Celtic folk singer Grace Griffith finally found some interest in releasing Cassidy's music at the label she recorded for, Blix Street. In April of 1998, Los Angeles-based Blix Street Records released Songbird, a posthumous album that featured tracks from Live At Blues Alley and Eva by Heart (a studio album released locally in the D.C. area in late 1997), along with Eva's re-defining version of "Over the Rainbow" from The Other Side (Eva's 1992 duet album with Chuck Brown). Despite making a number of noted music critics' year-end Top Ten lists in 1998 and earning Record of the Year honors on England's BBC Radio 2, the CD lingered in obscurity for a few years until being given airplay on the BBC. In 2001 both the album and the single "Fields of Gold" reached number one status in the U.K. Sting, the songwriter for "Fields of Gold" was reported moved to tears when he heard Cassidy's version of this song.

Eva Cassidy's recorded legacy continues. In March 2001 the ABC's "Nightline" (US) broadcast a well-received short documentary about Eva Cassidy. A similar broadcast occurred on ITV's "Tonight with Trevor McDonald" (UK) in May 2001. In 2002, figure skater Michelle Kwan brought Cassidy's music to a new audience when she skated to Eva's recording of "Fields of Gold" at the Winter Olympics gala (and then later on tour during the northern summer of 2002). In 2003, American Tune became Eva's third consecutive Number 1 album in the UK, something no other posthumous artist has ever done.