The new deal "means more responsibility", Sergio Conceicao told a news conference.
"I always have one essential thing in mind: the success of Porto professionally," he said, adding he was looking forward to "the return of the fans to the stadiums".
The 46-year-old Portuguese, who has coached Porto since 2017, and won two league titles, a Portuguese Cup and two Supercups, although the club finished second to Sporting in the top-flight last season and lost in the semi-finals of both domestic cups.
Before Porto, the former Portugal winger coached Nantes and several Portuguese clubs including Braga and Vitoria Guimaraes.
The decision to extend the contract was "very easy to take", said club president Jorge Pinto da Costa, adding that while Sergio Conceicao's salary "will not increase by one euro" the deal was not motivated by financial considerations.
