The band will release 'When She Was Mine' as their first official song through Polydor in the UK on May 27.
The accompanying music video was shot in Los Angeles and sees the group performing the track on a rooftop with the city skyline behind them.
'When She Was Mine' was produced by John Shanks, who has recently worked on Take That's Beautiful World and The Circus albums.
Lawson consists of frontman Andy Brown, lead guitarist Joel Peat, drummer Adam Pitts and bassist Ryan Fletcher.
> Lawson reveal behind-the-scenes pictures from new music video
> Ones to watch: Lawson
Watch the music video for Lawson's 'When She Was Mine' below: