The Viacom-owned free-TV broadcaster will now air Big Brother until 2018. The deal, with series producer Endemol Shine Group, means Channel 5 will broadcast broadcast two series of Celebrity Big Brother and one series of Big Brother each year.
Endemol Shine prodco Initial will make all of the shows.
The series perform well for Channel 5 and Viacom has also started putting out repeats on MTV UK.
Big Brother has been on Channel 5 for four years, having previously been on rival free-TV broadcaster Channel 4.
Nick Samwell-Smith, managing director of Initial, said: “Over the past four years we’ve worked closely [with Channel 5] to keep this extraordinary format feeling fresh, noisy, and creatively vibrant.
“I’m thrilled that this landmark deal means we can look forward to three more years of big characters and juicy storylines from inside our favourite house.”