The two sides have agreed to a five-year extension.
Fisher, a solid two-way centre, had 22 goals and 26 assists for 48 points in 68 games last season.
The 27-year-old has spent his entire career with the Senators after Ottawa selected him in the second round (44th overall) of the 1998 NHL entry draft.
Fisher, who was slated to become an unrestricted free agent next summer, will earn US$1.5 million dollars this season.
Ottawa forward Dany Heatley and defenceman Wade Redden are still slated for unrestricted free agency after the upcoming season.