Merloni was born on April 6, 1971, in Framingham, Massachusetts, the United States. His nickname is "Sweet Lou" given by Boston fans. He attended Providence College, where he graduated in 1993. As a baseball player, he has played for numerous single-season and has a career record for the now-defunct Friars baseball team.
During his 1994–95 Major League Baseball strike, Merloni was a replacement player. Therefore he was barred from membership in the Major League Baseball Players Association. He is well-known for hitting a home run in his first major-league at-bat in Fenway Park, a 3-run home run off of José Rosado.
At the beginning of the 2006 season in Triple-A, Merloni joined the Cleveland Indians on May 17, 2006, CC Sabathia has also played for the same team. He also made a contract with the Oakland Athletics for the 2007 season. After playing a season, he became the Most Valuable Player of Bricktown Showdown in 2007.
Merloni also led the River Cats over the Richmond Braves by a final score of 7-1. He also became the Best Defensive Player and Best Teammate for 2007 season. While playing, he contributed a home run and 4 RBI in the game. Before the game began, he was selected as the River Cats team captain.
In March 2008, Merloni started serving as a host on WEEI-AM's Big Show. In the same year, he joined the New England Sports Network (NESN) as a commentator on the Red Sox pre-game and post-game shows. At the end of 2008 season, he joined Comcast SportsNet New England as an analyst and reporter.
Later, Merloni started working on Red Sox radio, as a color analyst together with his team announcers Joe Castiglione and Dave O'Brien, where Ben Cherington has served as a general manager and executive vice president. In the same year, Merloni joined Castiglione and O'Brien for WEEI's broadcasts of the ALCS and World Series.
Merloni is an American by nationality and belongs to white ethnicity. He began dating his girlfriend, Steffanie Merloni. After dating her for sometimes, he married her and blessed with a son Mason Merloni. He lives a happy married life along with his spouse and children and has no any rumor of divorce between the couple.
Merloni is a well-known baseball player and host, who earns a huge amount of money from his professional career. He has worked as commentator and host for numerous shows from which he must have collected a decent amount of salary. However, his current net worth is under review.