Sky and BT have signed a deal to sell their channels on each other's platforms.
In addition, BT will be able to sell Sky's Now TV service - which includes Sky Sports, Sky Cinema and the Sky Atlantic channel - to its customers.
The new services will be available to customers from early 2019.
BT has spent more than £3.5bn on Champions League and Premier League football rights since 2012 in an attempt to compete with Sky.
Gavin Patterson, chief executive of BT, said: "This is an important day for BT and for our customers, who will be able to enjoy a whole range of Sky's sport and entertainment programming on their BT TV boxes.
"This is the next logical step for our TV and content strategy. We feel that now is the right time to broaden the ways in which we distribute BT Sport.
Sky boss Jeremy Darroch said: "This is great news for Sky customers who will be able to access all matches on Sky and BT channels from the Premier League, UEFA Champions League and Europa League directly with a single Sky TV subscription and with the great customer service that we provide."