The pair - Cameron Edwards and Joseph Lenzie - originally formed the group back in 2006 but have enjoyed an incredibly successful 2014 with two number one singles.
Nobody To Love, a reworking of Kanye West’s Bound 2 was a number one hit in over 10 countries and top 10 in another 35.
Changing, co-written with Ella Eyre and BMG Chrysalis writer Wayne Hector, featuring vocals by Paloma Faith was also number one in September. Both releases have received more than one million downloads to date.
The BMG deal comes ahead of the release of Sigma’s first album, expected early next year.
Joe and Cameron of Sigma said: ‘It's a great feeling to be with BMG and Primary Wave, who have both worked with so many amazing artists. Really looking forward to what we can achieve together.’
Josh Brandon, Sigma's manager, added: ‘Myself, Andy and the team are hugely excited to be working with Steve, Alexi and everyone at BMG as well as Justin, Jake, Ed and the team at Primary Wave. Both companies are achieving great things and it's a pleasure to become part of the family.’
Visit bmgchrysalis.com for more information.