Kevin Frandsen's journey through Major League Baseball began when he was drafted by the San Francisco Giants in the 12th round of the 2004 MLB Draft. A native of San Jose, California, Frandsen attended San José State University, where he honed his skills as an infielder. His time in the minor leagues was marked by steady progress, and he made his MLB debut with the Giants on April 28, 2006.

During his tenure with the Giants, Frandsen played primarily as a second baseman but also demonstrated his ability to fill in at various infield positions. His rookie season saw him appear in 41 games, where he batted .215. The following year, he played in 109 games, improving his batting average to .269 and hitting five home runs. Frandsen's versatility in the infield was an asset to the Giants, although his playing time fluctuated due to the team's roster dynamics.

In 2008, Frandsen's career faced a setback when he ruptured his Achilles tendon during spring training, causing him to miss the entire season. He returned to the Giants in 2009 but struggled to regain his form, resulting in limited playing opportunities. In March 2010, Frandsen was traded to the Boston Red Sox, but his time there was brief, as he was designated for assignment and subsequently claimed off waivers by the Los Angeles Angels of Anaheim.

Frandsen's stint with the Angels was short-lived, and he was released in June 2010. Shortly thereafter, he signed a minor league contract with the San Diego Padres but did not make an appearance for the major league team. In 2011, Frandsen signed with the Philadelphia Phillies, where he spent the majority of the season in the minors. However, he was called up to the majors in September, appearing in 13 games.

The 2012 season marked a resurgence for Frandsen, as he became a regular fixture in the Phillies' lineup following an injury to starting third baseman Placido Polanco. Frandsen seized the opportunity, playing in 55 games and posting a .338 batting average, which was a career high. His performance earned him a spot on the Phillies' roster for the 2013 season, during which he played in 119 games and batted .234.

In 2014, Frandsen signed with the Washington Nationals after being released by the Phillies. He played in 105 games for the Nationals, contributing primarily as a utility infielder and pinch hitter. Frandsen's time with the Nationals concluded after the 2014 season, and he signed a minor league contract with the Arizona Diamondbacks in 2015. However, he did not make the major league roster and was released in June of that year.

Throughout his MLB career, Frandsen was known for his adaptability on the field and his ability to step into various roles as needed.