Video assistant referees will be used in the Champions League from the 2019-20 season, Uefa has announced.
VAR will also be used in the 2019 Super Cup and at Euro 2020, as well as in the Europa League from 2020-21 and the 2021 Nations League finals.
The system - used widely at the 2018 World Cup in Russia - allows referees to review footage of key decisions.
President Aleksander Ceferin said Uefa was "confident" it would have time "to put in place a robust system".
He added it would also provide sufficient time to train match officials to ensure an "efficient and successful implementation of VAR" in "the world's flagship club competition".
VAR was under intense scrutiny at the World Cup, where its use was allowed to clear up incidents around the awarding of goals, penalties, red cards and in cases of mistaken identity.
Australia's A-League was the first top-flight league to use the system in 2017, with Major League Soccer in America soon following.
England's Carabao Cup will use VAR in all fixtures held at a Premier League ground this season.