Barca earned the Spanish King's Cup trophy, scoring all their goals in the second half of the final at La Cartuja Stadium, Seville. French star Antoine Griezmann scored the opener with a left-footed shot in the near post in the 59th minute to give Barcelona the lead.
Barcelona won the Spanish Cup 31 times to be the most successful club in the domestic tournament.
Athletic Bilbao lost their second Spanish Cup final in two weeks.
Real Sociedad bagged the 2020 Copa del Rey in a delayed final, beating Athletic Bilbao 1-0 in Seville on April 3.
The 2020 final was postponed because of the coronavirus pandemic.