Drafted at No. 6 by the Wild in 2001, their second year, Koivu 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. One night later he scored his first NHL goal in a 4-3 win against the Mighty Ducks of Anaheim, the first of six goals and 21 points he would score 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.