Fletcher wrote "On a Rainbow", the official song of the 2012 Summer Olympics' mascots Wenlock and Mandeville. The song features vocals from him and his sister Carrie Hope Fletcher. He also wrote the song "I Want" for One Direction's debut album "Up All Night", and co-wrote (with Dougie Poynter and Danny Jones) "I Would" for their second album "Take Me Home" and "Don't Forget Where You Belong" for their third album "Midnight Memories". He has co-written several songs with James Bourne including "Chills in the Evening", recorded by V. He also co-wrote "High Hopes" along with all four members of the Vamps for their debut album, "Meet the Vamps". Fletcher is also credited as having co-written the 5 Seconds of Summer track "Try Hard". The song was originally released on YouTube on 1 June 2013, and in 2014 featured as a B-Side to their hit single "Don't Stop".