He competed on the Professional Bowlers Association (PBA) tour in the United States, and won bowling titles in 21 different countries during his career.

On April 15, 2011 Koivuniemi captured the championship in the 2011 World Bowling Tour (WBT) Finals in Las Vegas, Nevada.

As the #1 seed for the three-person stepladder final, Koivuniemi earned the WBT title by defeating Sean Rash of the USA 237–224 in a single-game match.

[6] Mika has won bowling titles in 21 different countries (Austria, Bahrain, Canada, China, Colombia, Denmark, England, France, Germany, Japan, Korea, Malaysia, Netherlands, Qatar, Singapore, Slovenia, Spain, Sweden, Thailand, USA, and his home country of Finland).

An extremely versatile bowler, he was the first player to win a title on all five of the PBA's "animal" oil patterns (Shark, Chameleon, Cheetah, Scorpion and Viper) – a feat matched only by Tommy Jones so far.

In addition, Koivuniemi's opponent in that match, Tom Daugherty, scored 100, so the margin of victory (+199) was the largest in Tour history.

[10] Koivuniemi went on to roll ten more strikes in the final match to defeat top seed Tom Smallwood, 269–207, for the major championship.

His 14th and most recent PBA Tour title was earned at the 2014 Viper Open, part of that year's World Series of Bowling in Las Vegas.

The opportunity to coach the bowling team of the United Arab Emirates and the need to rehab from back and knee injuries were the main factors in his decision.

He was the #2 qualifier after the first 24 games,[5] moved up to the #1 seed after the match play round, and won the tournament on June 15 for his first PBA50 Tour title.

[14] Koivuniemi was again the top qualifier at the 2019 PBA Senior U.S. Open, but this time he lost the title match to Norway's Tore Torgersen in an all-Scandinavia final.

While born and raised in Finland, Mika resided in Hartland, Michigan, USA during his full-time PBA Tour years.