In 2012, Marcus & Martinus were contestants on the eleventh season of Melodi Grand Prix Junior. It was held at the Oslo Spektrum in Oslo, Norway and was broadcast live by Norwegian Broadcasting Corporation (NRK), hosted by Margrethe Røed and Tooji. They won the contest with the song "To dråper vann" (English: "Two Drops of Water"). The song peaked to number 8 on the Norwegian Singles Chart.
On 23 February 2015, they released their debut studio album Hei (English: Hi). The album peaked at number 1 on the Norwegian Albums Chart in week 46 of 2015 (15 November 2015) after having charted for 35 weeks, the last 20 not leaving the top ten. The album includes the single "Plystre på deg" (English: "Whistle at You"). On 24 July 2015, they released the single "Elektrisk" (English: "Electric"), featuring vocals from Katastrofe. The song peaked at number 3 on the Norwegian Singles Chart. On 25 September 2015, they released the single "Ei som deg" (English: "One Like You") with Inner Tier. The song peaked at number 15 on the Norwegian Singles Chart.
In May 2016, the duo released three singles. The first, "Girls", featuring Madcon, debuted at number 1 in Norway and became their second single to reach the top 100 in Sweden after "Elektrisk". The second and third, "Heartbeat" and "I Don't Wanna Fall in Love", followed just days after the release of "Girls" and debuted at numbers 21 and 37, respectively. They followed up "Girls" with the singles "Light It Up" and "One More Second".
In November 2016, they released their first English album titled Together. The album includes their hit songs "Girls", "Heartbeat", "Light It Up" and "One More Second". In the week after its release, Together debuted at number 1 in Norway and Sweden and number 6 in Finland.
As the Young Talent Act of the 2016 Nobel Peace Prize Concert, they performed "Without You" and "Bae" at Telenor Arena in Norway on 11 December 2016 (2016-12-11).
On 9 May, it was announced that they would be the spokespersons for Norway in the international Eurovision Song Contest 2017 final, on 13 May.
On July 14th they performed on Swedish Crown Princess Victoria's 40th birthday with their own song written especially for her ("On This Day").
On May 21th, 2017, they released their new single "Like It Like It" alongside singer Silentó.
On July 1, 2017, they released "First Kiss."
On the 28th of that same month, they released their new single "Dance With You".Film
Together Tour (2016–2017)