He worked as a security guard in McDonald's and as a bingo caller before finding fame with Westlife McFadden's main interests have always been singing, dancing and football. Together with his sister he attended "Billie Barry Stage School'" in Dublin and performed as an actor onstage all major theatres in Ireland. He also had a role in the Irish TV show "Finbar's Class", a comedy about a group of teenagers set in a school. In 1998 he started a pop and R&B-influenced group called Cartel with two other boys named Tim and Darragh. Together they performed live in many of Dublin's pubs.

During 1998/1999, Brian dated Aquasinger, Lene Nystrøm Rasted. McFadden married Kerry Katona on 5 January 2002. They have two daughters: Molly Marie McFadden and Lilly-Sue McFadden. Brian was voted Celebrity Dad of the Year in 2002, and Kerry was crowned Best Celebrity Mum in 2002 and 2004. Katona and McFadden announced their separation in September 2004 and their divorce was finalized in December 2006.

McFadden is now engaged to Australian singer and actress Delta Goodrem with whom he collaborated on the duet "Almost Here". Initially, the couple denied being romantically linked. After breaking up with Kerry, he claimed Delta was 'helping him' get over the pain, and the two shared many long phone calls until McFadden admitted the relationship. On November 29 2007, Brian announced his engagement to Goodrem.

Brian departed from Westlifeafter the release of the album Turnaround. With Westlife McFadden sold more than 30 million albums and 7 million singles, had 12 #1 singles in the UK chart and sold out arenas all over the world. Some of Westlifes songs were co-written by McFadden, such as Fragile Heart(from the album "Coast to Coast"), Bop Bop Baby, I Wanna Grow Old With You and Love Crime (from the album "World of Our Own"). He gained a reputation as quite the comedian. On the eve of the Turnaround tour, McFadden left Westlifeon 9 March 2004 to spend more time with his family and work on solo projects. His final public performance as part of Westlifewas at Newcastle Upon Tyne's Powerhouse nightclub on 27 February 2004.

In July 2004 McFadden was signed to the major record company Sony BMG. In September he released his debut single "Real to Me", which went straight to #1 on the UK charts. His first album Irish Son charted in the Top 30 of the UK charts. Most of the songs were co-written with Guy Chambers, best known for his successful collaboration with Robbie Williams and Inxs His second single, "Irish Son", released in November 2004 went to #6 on the UK charts. The third single, "Almost Here", a duet with Australian singer Delta Goodrem peaked at #3 on the UK charts and reached #1 in Australia in 2005.

McFadden's latest single “Like Only A Woman Can” was released in Ireland on April 20, 2007 and reached the Number 1 position on the Irish Singles Chart. It reveals a grown up, more mature McFadden. The self-penned song is the first track from his yet untitled second solo album, McFadden describes it as being about his relationship with Delta Goodremand he also said the song was about his mother and sister and women in general, and admitting mistakes in the past whilst looking forward to the future.