Brown and the Senators agreed to terms before both sides were set to head to arbitration, with the 26-year-old's hearing scheduled for Thursday.
Later announced by the club, Brown's new contract will pay him $2.8 million next season, $4 million in 2021-22 and $4 million in 2022-23.
Brown excelled in Ottawa after the July 2019 trade that sent him to the Senators, posting 16 goals and 43 points through 71 games in 2019-20.
Through five seasons as part of the Toronto Maple Leafs organization, Brown amassed 43 goals and 99 points in 253 games at the NHL level, and another 90 points through 110 games for the AHL's Toronto Marlies.
“We’re very happy to have Connor back under contract,” Senators general manager Pierre Dorion said via a team release. “He brings a veteran presence to our lineup and is a player who can play in different situations. He’s durable, has a strong work ethic with great practice habits and is regarded as a leader by his teammates.
"His ability to play up and down the lineup while producing offensively is especially valuable to us as we continue our transition towards being a consistent winner.”
Having inked his new deal, Brown slots in as the fourth-highest paid forward on the Senators roster, after Evgenii Dadonov ($5 million cap hit), Colin White ($4.75 million), and Artem Anisimov ($4.55 million).