The new deal will also extend to Channel 5 and its sister channels, including 5USA.
The arrangement means Viacom’s pay-TV channels, which include Comedy Central, MTV and Nickelodeon, will continue to be available on Sky.
David Lynn, the president of Viacom International Media Networks for the UK, Australia and Eastern Europe, said: "Sky is a highly-valued partner for Viacom and we’re delighted to extend our relationship for the benefit of our viewers and advertisers.
"We’re convinced Viacom’s interests are best served by a single point of advertising sales in the UK and Ireland and that Sky Media, with its strong track record of selling our pay-TV channels and its innovative approach to improving the targeting and effectiveness of TV advertising, is best placed to provide it."
Andrew Griffith, the chief financial officer and managing director of Commercial Businesses at Sky, said: "The extension of our partnership with Viacom is great news for Sky customers as well as advertisers.
"The addition of Channel 5 will further strengthen Sky Media’s extensive channel portfolio. Advertisers will now have access to an even broader range of opportunities to reach customers using Sky Media’s creativity and innovation."