The deal comes as Giroux was entering the final year of his contract and with the Flyers in the midst of reshaping a team that missed the playoffs last season.
A two-time 25-goal scorer, Giroux is the Flyers' top play-making offensive threat. He had 13 goals and 35 assists for 48 points in 48 games last season.
Overall, he has 291 points (91 goals, 200 assists) in 333 career games spread over six seasons in Philadelphia.
"Claude is a high-quality young man that over the past few years has blossomed into our best player and also one of the top players in the league. We look forward to more and better things to come," said general manager Paul Holmgren, in a statement.
The Flyers have already made several splashes over the past two weeks. They landed this summer's most high-profile free agent by agreeing to terms with Vincent Lecavalier on a four-year contract Tuesday. Lecavalier was available after the Tampa Bay Lightning bought out the remaining years on their captain's contract.
Philadelphia was also aggressive in freeing up salary cap space. The team bought out the contracts of forward Danny Briere, who has agreed to a deal with Montreal, and goalie Ilya Bryzgalov.
The Flyers also announced on Thursday that they will re-sign journeyman center Adam Hall to a one-year deal. The Flyers acquired Hall by claiming him off waivers in April.