The Guardian compared the musician to such celebrities as Ross Copperman, Frankmusik, and the band Keane. In the summer of 2009, the artist released his debut LP, Hassle. It climbed to the 2nd spot of the Swedish chart and stayed there for 10 weeks. The second single from the album, "Don't Bring Flowers", became a hit and reached the 25th spot on the charts.
In 2010, Erik rereleased his debut album in the UK. It was renamed to Pieces. Even though the album didn’t appear in the charts immediately, it became popular. Popjustice magazine put the LP on the 11th spot of its main releases of the year list. At that time, many fans tried to book Erik Hassle for private events.
In January 2010, Hassle performed at the finals of the Danish version of X-Factor. He was also called the Newcomer of the Year 2009 at the Swedish music awards, P3 Guld. The next year, he got a prize at the Grammis.
In the spring of 2010, Erik’s song “Hurtful” became the single of the week at iTunes store. Three months later, the singer released an EP, The Hassle Sessions: Volume One, which featured cover versions for popular songs.
In 2011, while working with two artists from the group Kent, Erik presented one more EP, Mariefred Sessions.
In 2012, he released a new LP, We Dance, with the assistance of Roxy Recordings.
In 2013, Hassle moved to LA and help write the lyrics for Shakira’s single “Can't Remember to Forget You”, which was recorded with Rihanna. The track made it into the top-10 of numerous charts in Europe. In the USA, it debuted on the 15th spot of Billboard Hot 100. For the first time, Erik wrote a song for someone else.
The next EP came out in March 2014. Hassle called it Somebody's Party. It was released with the assistance of Ten / RCA Records. The album featured six songs. All of them were recorded as R&B tracks. While making one of the singles, "Talk About It", Erik invited a rapper from Chicago, Vic Mensa.
After coming back to Sweden, Hassle started working on a new song “No Words”. In one of the interviews with Billboard Magazine, the singer said that he was recording the song while feeling heartbreaking pain. The single came out in 2015 and became a huge hit. It made it into the top-10 of many charts in the United States and became golden in Sweden.
In January 2017, with the assistance of TEN / RCA Records, the singer recorded his next LP, Innocence Lost. It featured 12 new songs. The single “Missing You” became a hit.
Critics often compare Hassle’s talent to those of Michael Jackson and Prince. He co-wrote and helped record a hit song “Emergency” released by a popular Swedish group Icona Pop. The song topped the Billboard Dance Club Songs Chart. It was used for the videogame, FIFA 16.