Video Assistant Referees will be used in the Champions League from the knockout stages of this season's competition and in the Nations League finals in June, UEFA confirmed on Monday.
European football's governing body had previously stated its intention to introduce VAR only from the start of the 2019/2020 season.
"If we can do it before, why wait? We cannot afford any mistakes if we can do it earlier," said UEFA president Aleksander Ceferin after a meeting of the European football body's Executive Committee.
"We are ready to use VAR earlier than initially planned and we are convinced that it will be beneficial for our competitions as it will provide valuable help to match officials and will allow to reduce incorrect decisions."
VAR is already used in a number of Europe's top leagues, including Spain's La Liga, Germany's Bundesliga and Serie A in Italy and was widely seen as a success at this summer's World Cup.
The Europa League final and the under-21 European Championships in Italy in June will also use VAR.