The Minnesota Wild, coming off their first NHL season, selected Koivu with the No. 6 pick in the 2001 NHL Draft, and he became Minnesota's captain in 2009.

The younger brother of former Montreal Canadiens captain Saku Koivu and son of former Finnish elite league coach Jukka Koivu, Mikko made his Wild debut in a 3-1 win over the San Jose Sharks on Nov. 5, 2005. He scored his first NHL goal one night later in a 4-3 win against the Mighty Ducks of Anaheim and finished with 21 points (six goals, 15 assists) in 64 games that season.

A gifted skater with the same tenacity of his older brother, Koivu established himself as one of the top two-way centers in the NHL in his second year. He played all 82 games in 2006-07 and had 20 goals and 54 points while earning his first votes for the Selke Trophy, awarded to the NHL's best defensive forward.

Over the next three seasons, Koivu scored 20 goals twice. He broke his leg early in the 2007-08 season, forcing him to miss 24 games, but he finished eighth in Selke voting that season and tied for fourth the next.

Koivu recorded his 500th career point on April 9, 2015, making him the first Wild player and the 10th Finnish player to reach that mark in the NHL.

During the 2015-16 season Koivu broke Nick Schultz's team record of 743 games played. He reached two milestones on Dec. 1, 2019, becoming the first player in Wild history to play in 1,000 games and the first to reach 700 points.

Koivu initially considered retirement following the 2019-20 season when the Wild decided to not re-sign him, but he signed a one-year contract with the Columbus Blue Jackets. He scored two points (one goal, one assist) for them before retiring Feb. 9, 2021.

Koivu had his No. 9 retired by the Wild before their game against the Nashville Predators at Xcel Energy Center on March 13, 2022. He was the first player in team history to have his number retired; Minnesota retired No. 1 for its fans prior to its first NHL game Oct. 11, 2000.