Her first album was released in 2000. Her most notable role was Mara in the 2002 film The Time Machine. She has also appeared in a number of Irish independent films.

Mumba was born at Palmer Street Hospital in Dublin, Ireland. Her father, Peter Mumba, is a black Zambian and was formerly an aircraft engineer, and her mother is a white Irish woman. Mumba attended Dublin's Billie Barry Stage School from the age of three to fifteen. When Mumba was 15 she was discovered on an RTÉ TV talent show Let Me Entertain You by Irish music Svengali Louis Walsh (manager of Boyzone and Westlife). Walsh was impressed by her talent and she was signed to Polydor Records. She subsequently spent several months moving between Denmark, Sweden, the UK and Ireland where she co-wrote and recorded her debut album, Gotta Tell You. She eventually dropped out of school to focus on her music career, explaining that it was becoming difficult to stay in school and work on her music.

Mumba recently became engaged to actor Ruaidhri Conroy.

Samantha sings contralto. Mumba's first single, "Gotta Tell You", was released in 2000 and reached No. 1 in the Irish charts. It later reached No. 2 in the British charts. Mumba also had success in the USA, with the song peaking at No. 4 on the Billboard Hot 100. The album Gotta Tell You stayed on the charts for six months and was eventually certified platinum for sales of 1 million copies. Five more Top 10 hits followed in the UK and she had another top 50 hit in the US. Another hit from this album was "Baby, Come Over (This Is Our Night)" which was a remixed version of "Baby Come On Over" and features on the US edition of the album. To date, her first album has sold over 4 million copies worldwide. In 2001 Mumba contributed to the track "You Raise Me Up" by the Celtic Tenors. An EP was also released in 2001 at Christmas called Samantha Sings Christmas; it is also a bonus disc on rare special editions of Gotta Tell You.

In 2002, Mumba released a new single "I'm Right Here" with a slightly more laid-back sound. The video features Damien Marley, son of Bob Marley. The video was a television favorite in both the US and UK. The single became Mumba's fifth UK top 5 single and her fifth top 40 single in Ireland. In the US and Germany, the song was less successful, peaking at 80 and 81.

Rumors circulated that Mumba was getting ready to release a second album, Woman, but due to the poor sales of the lead single "I'm Right Here" in the US and a short lived time on the UK chart, she was dropped from her label, but Mumba stated on the Late Late Show (February 3, 2007) that there never was a second album, and the tracks leaked on the internet were attempts by her to find a new sound.

In December 2005, she collaborated with Filipino R&B singer Jay-R to sing Just the Way You Are.

On October 23, 2006, a compilation album, The Collection, was released. The album features songs from Gotta Tell You, B-sides and two new tracks including her single "I'm Right Here".

The singer sold just a handful of tickets for a highly-publicised comeback concert in her home town, Dublin, which lead to it being cancelled in February 2007.

On 17 January 2008, Samantha appeared on UK daytime TV show Loose Women. After discussing her time away from the music scene, and her appearance on ITV reality TV show Dancing On Ice which ended abruptly after three weeks, the singer stated that she had almost finished recording her new album, and hoped it would be released in the summer of 2008.