Brian Dowling won the £70,000 Big Brother 2 prize
It will return for Big Brother 3 this summer - and the new deal means it should keep coming back until Big Brother 6.
Producers have denied reports the 10 contestants who will be seen sharing the house this year have already been chosen.
The final line-up will not be settled upon until just before they go into the house, where cameras will watch their every move.
More than 150,000 people applied to be on this year's show - twice as many as in 2001.
Channel 4 have refused to confirm speculation that this year's house will be split into "luxury" and "basic" sections.
Spin-offs
Details of the Big Brother 3 set-up will be revealed in early May, with the show starting either later that month or in early June.
Channel 4 has signed the four-year deal with the show's producers Endemol.
It also paves the way for more spin-off shows like Celebrity Big Brother, which was shown jointly with the BBC as part of last year's Comic Relief appeal.
Viewers will be able to watch Big Brother 3 through interactive TV services, as well as on Channel 4 and live internet broadcasts.
Gerry Bastable, who negotiated the deal for Channel 4, said Big Brother was still the best example of a show that works well across a range of media.
"Big Brother has enjoyed phenomenal success across all platforms with record ratings on Channel 4 and E4 and a record response from viewers via interactive TV, the web and phone voting," he said.
Millions of viewers
The show, which first appeared in the Netherlands in 1999, throws 10 strangers together in one house.
They are unable to leave until they are voted out by their housemates and the public.
One person leaves every week, and the one remaining at the end is the winner.
More than seven million people tuned in to see Brian Dowling win the £70,000 first prize in 2001, and ten million saw Craig Phillips win the first UK series in 2000.