The broadcaster has announced that commercial and residential premises can tune in to BT Sport Showcase - Freeview channel 59 - BT Sport Europe on Sky 414 or even YouTube to air the final.
Real Madrid are taking on arch rivals Atletico Madrid at 7:45pm on 28 May, part of a bumper bank holiday weekend for licensees.
BT said the move is part of an ambitious plan to bring its sport channels to millions of additional fans, including on social media and mobile.
More than five million homes now subscribe to BT Sport channels and the service is available in over 27,000 commercial premises.
The move follows TalkTalk’s announcement earlier this week that BT Sport will be available to TalkTalk TV homes from next season.
EE, the UK’s biggest 4G mobile network provider and part of BT Group, will also introduce a new offer to bring BT Sport to millions of EE customers in time for the start of the next football season.
John Petter, chief executive of BT Consumer, said: “We want to make sure that millions more sports fans can join in from next season, accessing content digitally, whether that’s through social media, mobile devices or digital TV.
“BT Sport has pioneered the way when it comes to new technologies and digital platforms, whether that’s live Ultra HD, our immersive BT Sport App or red button functionality on YouView.
"There’s plenty more that we’re looking at, whether that’s more programming in live Ultra HD, new App developments or our recent Virtual Reality trials at the FA Cup semi-finals and NBA.”
BT also plans to drive social media engagement across YouTube, Snapchat, Facebook, Instagram, Twitter and Vine.
Petter continued: “We’ve always said we wanted to give top quality sport back to the people and making the UEFA Champions League and Europa League finals free to everyone in the UK does this in a big way.
“We’re also bringing BT Sport to a new generation of younger sports fans who view their entertainment online, through social media and on their mobile devices.”
The Manchester City semi-final second leg against Real Madrid had an audience peak of 1.7m.
BT Sport also made the Europa League final, in which Liverpool lost to Sevilla, available to all.