The 20-year-old will join the Spanish club on 1 July until the end of the 2025 season and his contract has a 500m euro buy-out clause.
Portugal Under-21 international Trincao made his debut in his country’s top-flight in January 2019.
He has made 11 league appearances for Braga this season, scoring twice and managing two assists.
Later on Friday, Barcelona announced the signing of 21-year-old Brazilian midfielder Matheus Fernandes from Palmeiras for an initial fee of seven million euros (£5.8m) with three million euros (£2.5m) in add-ons.
He will join on 1 July on a five-year deal with a 300m euro (£251m) release clause.
Fernandes has scored once in 11 matches since joining Brazilian side Palmeiras from Botafogo last year and he has represented Brazil’s under-17 and under-20 sides.