Mike Mordecai's journey in Major League Baseball began when he was drafted by the Atlanta Braves in the sixth round of the 1989 MLB Draft. His professional debut came in 1994 with the Braves, where he played as an infielder. Mordecai's role with the Braves was primarily as a utility player, providing depth to the infield positions. During his time with Atlanta, he was part of a team that consistently competed at a high level, including their World Series win in 1995, although his contributions were more supportive than starring.

In 1998, Mordecai was traded to the Montreal Expos, where he found more opportunities to showcase his skills. With the Expos, he played multiple infield positions, including second base, third base, and shortstop. His ability to adapt to various roles on the field made him a valuable asset to the team. Mordecai's time with the Expos allowed him to gain more playing time and demonstrate his capabilities as a reliable infielder.

The next significant chapter in Mordecai's career came in 2002 when he joined the Florida Marlins. It was with the Marlins that he experienced one of the highlights of his career. In 2003, the Marlins made a remarkable run to the World Series, and Mordecai played a part in their success. During the National League Championship Series against the Chicago Cubs, Mordecai delivered a crucial three-run double in Game 6, helping the Marlins overcome a deficit and eventually win the series. The Marlins went on to win the World Series, defeating the New York Yankees, and Mordecai earned his second World Series ring.

Throughout his career, Mordecai was known for his defensive skills and his ability to play multiple positions. While he may not have been a regular starter, his role as a utility player was essential for the teams he played with. His career batting average was .244, with 24 home runs and 132 RBIs over 12 seasons in the major leagues. Mordecai's career concluded after the 2005 season with the Marlins.

After retiring as a player, Mordecai transitioned into coaching and player development roles.