The first records Benny bought were "Du Bist Musik" by Italian schlager singer Caterina Valente and Elvis Presley's "Jailhouse Rock".

In October 1964 he joined the Hep Stars as keyboardist and they made a breakthrough in March 1965 with their hit "Cadillac", eventually becoming the most celebrated of the Swedish 1960s pop bands.

Andersson met Björn Ulvaeus in June 1966, and the two men started writing songs together, their first being "Isn't It Easy To Say", eventually recorded by the Hep Stars.

The personal relationships and Andersson and Ulvaeus' songwriting collaboration led quite naturally to the very close cooperation which the four friends had during the following years.

As the two couples began supporting each other during recording sessions, the sound of the women's voices convinced the songwriters to model their 'group' on various MOR acts such as Blue Mink, Middle of the Road and Sweet.

The Chess concept album – with vocals by Elaine Paige, Barbara Dickson, Murray Head and Swedes Tommy Körberg and Björn Skifs – was released in October 1984, selling two million copies worldwide.

Chess was staged in London's West End Prince Edward Theatre in May 1986 and received mixed to positive reviews, running for about three years.

[4] Andersson composes primarily for his band BAO, with vocalists Sjöholm and Körberg, but he keeps his older material alive by re-visiting it, as in Mamma Mia!

For a compilation album of the Glenmark duo Gemini, Andersson had Björn Ulvaeus write new Swedish lyrics for the re-recording of two songs from 1984 and 1987.

In July 2009, BAO, now named "The Benny Andersson Band", released their first international record, the album The Story of a Heart.

In 2008, Andersson and Ulvaeus wrote a song for Swedish singer Sissela Kyle, titled "Jag vill bli gammal" ("I Wanna Grow Old"), for her Stockholm stage show "Your Days Are Numbered", which was never recorded and released but did get a TV performance.

Ulvaeus also contributed lyrics to ABBA's 1976 instrumental track "Arrival" for Sarah Brightman's cover version recorded for her 2008 album A Winter Symphony.

New English lyrics have also been written for Andersson's 1999 song "Innan Gryningen" (then also named "Millennium Hymn"), with the new title "The Silence of the Dawn" for Barbara Dickson was performed live, but not yet recorded and released.

In 2007, they wrote the new song "Han som har vunnit allt" ("He Who's Won It All") for actor and singer Anders Ekborg.

Ulvaeus wrote English lyrics for two older songs from Andersson's solo albums I Walk with You Mama ("Stockholm by Night", 1989) and After the Rain ("Efter regnet", 1987) for opera singer Anne Sofie Von Otter, for her Andersson tribute album I Let the Music Speak.

As of October 2012, Ulvaeus had mentioned writing new material with Andersson for a BAO Christmas release (also mentioned as a BAO box), and Andersson is busy writing music for a Swedish language obscure musical, Hjälp Sökes ("Help is Wanted") together with Kristina Lugn and Lars Rudolfsson, premiering 8 February 2013.

The song "Kärlekens Tid", recorded 2004 by Helen Sjöholm with BAO, has also been performed in concert in English (lyrics by Ylva Eggehorn) by opera baritone Bryn Terfel.

On 15 April 2013, it was officially announced by the EBU and the SVT that Andersson, along with Ulvaeus and the late Stockholm based DJ and record producer Avicii, had composed the anthem for the 2013 Eurovision Song Contest.

"Kärlekens Tid" was produced in Andersson's Mono Music studio, under the direction of choirmaster Gustaf Sjökvist, who died before the album's release.

Gustaf Sjökvists Choir, conducted by Cecilia Rydinger Alin, performed two concerts at Skeppsholmen on 20 September, featuring Benny Andersson on piano.

The new record, their first studio album in 40 years, features ten tracks, including "I Still Have Faith In You" and "Don't Shut Me Down", which also were first shown in the aforementioned livestream event and released as a double A-side single.

Andersson has written music to several films for screen and television; the first attempt in the early 1970s for the Swedish erotica movie The Seduction of Inga; the film was not a success, but the 'Björn & Benny' single "She's My Kind of Girl" surprised the composers by being released in Japan and becoming a Top 10 hit (the song renamed in Japan as "The Little Girl of the Cold Wind").

In 2002, Andersson was given an honorary professorship by the Swedish Government for his "ability to create high-class music reaching people around the world".

On 15 March 2010, Andersson appeared on stage in New York with former wife Anni-Frid Lyngstad to accept ABBA's award of induction into the Rock and Roll Hall of Fame.

[11] On 21 March 2024, all four members of ABBA were appointed Commander, First Class, of the Royal Order of Vasa by His Majesty King Carl XVI Gustaf of Sweden.

This was the first time in almost 50 years that the Swedish Royal Orders of Knighthood was bestowed on Swedes, also the 50th anniversary of ABBA winning the Eurovision Song Contest.

In the 1990s, their son Peter Grönvall formed One More Time, a group that enjoyed European success with the ABBA-like "Highland" and, later, as Sweden's entry to the Eurovision Song Contest 1996.