Mike Fisher grew up playing hockey in the Peterborough Minor Hockey Association (OMHA) with the Minor Petes. He was a 2nd round selection of the Sudbury Wolves (OHL) in the 1997 OHL Priority Selection while playing Tier 2 in Peterborough (OHA). He was then drafted in the second round (44th overall) of the 1998 NHL Draft by the Ottawa Senators. It was a thrill for Mike to be drafted by an NHL team so close to his home. He played his first season with the Senators in 1999/00. Unfortunately, his year was cut short by a season ending injury that limited him to only 32 games that year. Over the next several seasons, Mike became an integral part of the Senators team, eventually becoming an Assistant Captain.

During the NHL lockout year in 2004/05, Mike joined EV Zug of the Swiss Elite League. He recorded 27 points in 21 games that year. Mike played for Team Canada at the 2005 World Championships.

Mike is known for his aggressive play, but he has also shown a great deal of speed and skill. He holds Ottawa's unofficial hardest shot record at 105 mph. In the 2005-06 season, Fisher had a career year, setting new personal bests with a plus-minus rating (+/-) of +23, 64 penalty minutes, 149 shots on goal and 14.09% shooting percentage in just a mere 67 games, helping the Senators to finish the regular season atop the Eastern Conference standings. Though the Senators fell to the Buffalo Sabres in the second round in five games, he was the runner-up for the Frank J. Selke Trophy as best defensive forward (awarded to Rod Brind'Amour).