Barca extended Pique's deal until June 2024, Ter Stegen's until June 2025, De Jong's until June 2026, and Lenglet's until June 2026.
The agreements "include a temporary salary adjustment due to the current circumstances brought about the COVID-19-induced crisis," the club said in a statement.
The announcement came shortly after Barcelona's 5-1 win over Ferencvaros in the Champions League group stage.
Pique's extension is contingent on the Spaniard making a certain number of appearances during the 2021-22 season. He'll be 37 years old by the end of the new contract.
Talks over Ter Stegen's future persisted for months. Club president Josep Maria Bartomeu said in July he was hoping to persuade the keeper to sign a new deal, "not only for his quality as a goalkeeper but for his personality."
"He's a pillar of the dressing room and of the future," Bartomeu added. "At 28, he's one of the three best (goalkeepers) in the world."
Ter Stegen's previous contract was set to expire in June 2022.
De Jong, who's in his second season with Barcelona, is expected to be ever-present in Barcelona's lineup. The Dutch midfielder has already made 47 appearances with the squad and has started every match under manager Ronald Koeman.
Lenglet's made 89 appearances since joining the Catalan side from Sevilla in 2018.