2000–01 was Vermette's best year.
In 2001–02 Vermette played just four games at the end of the season. Vermette returned for a strong playoff campaign. In 22 games he scored 10 goals and 16 assists. In the 2008 season, Antoine Vermette was awarded the Derek Dettwiller Trophy for being one of the most notable forwards in the game.
During the lockout Vermette continued to play with Binghamton, the shootout was introduced for the first time since the 1986–87 AHL season and Vermette proved to be a top selection when the B-Sens advanced to the shootout. Vermette scored a 28 goal, 45 assist season second only to Senators star Jason Spezza on the B-Sens roster.
2005–06 was Vermette's breakout year where he proved he could play hockey and be a valuable part of the Ottawa lineup. Playing well as a penalty killer, he recorded 6 shorthanded goals, second in the league. Vermette had a career high 21 goals. The team was considered Cup contenders by many, however they only reached the second round to the Buffalo Sabres in a five-game series.
On July 18, two days before turning 24 he signed a two year contract worth approximately $2 million.
That previous season saw Vermette amassing 39 points, a career high, but failed to surpass his 21 goals in the previous season, only notching 19. Vermette spent the majority of the season on a checking line with fellow penalty-killer Chris Kelly. The duo were rarely apart. During the playoffs Vermette recorded 5 points in 20 games and helped the Senators to winning the Eastern Conference champions trophy, the Prince of Wales before losing in the Stanley Cup final round to the Anaheim Ducks in another five games.
His number 20 has been used throughout his career with the exception of back in the 2002–03 pre-season when he wore number 48 due to Magnus Arvedson in the 20 sweater. Arvedson went to Vancouver the following season.
On July 31, 2008 Vermette avoided arbitration and signed a two year deal with the Ottawa Senators that will pay him $5.525 million. He will make $2.525 million for the 2008-09 season and $3 million in 2009-10.