He is the lead singer of the indie pop band fun., and previously of The Format.As of 2015, he also performs as a solo musician.
Ruess released his first single from his debut album, titled Nothing Without Love, which was sent to the alternative radio on February 23, 2015. On April 6, 2015, Ruess announced his debut album would be called Grand Romantic, and it was released on June 16, 2015. On April 27, 2015, Ruess released the opening track from his debut album Grand Romantic, titled 'AhHa'.On June 1, 2015, Ruess released a new track from his solo album "Grand Romantic", titled "What This World Is Coming To". In 2018, Ruess was credited as a composer and lyricist for Keith Urban on his release Graffiti U. In 2019, he collaborated again with Pink for the track “Walk Me Home”, which was released in February for her upcoming studio album.