The decision was taken at a meeting of the UEFA Executive Committee at the House of European Football in Nyon on Thursday morning.
VAR will be introduced from the play-off stage of next season's UEFA Champions League. It will be used additionally for the 2019 UEFA Super Cup in Istanbul, as well as for UEFA EURO 2020.
UEFA subsequently plans to introduce it in the UEFA Europa League from the group stage of the 2020/21 edition, with the system also set to be in place for the 2021 UEFA Nations League Finals.
UEFA President Aleksander Čeferin said: "We are confident that introducing Video Assistant Referees in August 2019 will give us enough time to put in place a robust system and to train match officials to ensure an efficient and successful implementation of VAR in the UEFA Champions League, the world's flagship club competition."
Various other decisions were made by the UEFA Executive Committee concerning UEFA competitions.