Massarotti joined the Boston Herald in 1989, and covered the Boston Red Sox for the paper from 1994 through 2008.

During his time with the Herald, Massarotti frequently covered the Boston Red Sox for Fox Sports New England, and appeared occasionally as a guest on WHDH's Sports Xtra. He also appeared on Boston's WEEI sports talk radio program The Big Show. These appearances ended with his later leaving the Herald for the Boston Globe due to a long standing ban on Globe staffers appearing on the station..

While with the Herald, Massarotti was known for his staunch support of former Red Sox managers Jimy Williams and Grady Little, despite Little's controversial decisions, during Game 7 of the 2003 American League Championship Series.

In September 2008 Massarotti joined the staff of the Boston Globe. In addition to writing a regular column for the paper, Massarotti will become the voice and face of the Globe's online Boston.com sports feature.

Tony is now the co-host of Felger and Massarotti on WBZ-FM. He also appears on the The Toucher and Rich Show as "Naughty" Massarotti

Theo Epstein contract negotiations

On October 27, 2005, Massarotti published a column in which he accused Larry Lucchino and the Red Sox management of smearing Red Sox General Manager Theo Epstein during contract negotiations. In the column he also suggested that coverage of the negotiations at two local media outlets was compromised. He documented that the New York Times (parent company of the Boston Globe) owned a 17 percent ownership stake in the Red Sox and that local sports talk radio leader WEEI was currently in negotiations for Red Sox broadcast rights and paid Lucchino for a weekly radio appearance. The timing of the column was notable as it came 4 days after Globe ombudsman Richard Chacón published an article in which he criticized Times management for accepting 2004 World Series rings from the Red Sox, and 3 days prior to a Dan Shaughnessy column in which he revealed information detailing nuances of the relationship between Epstein and Lucchino, to the favor of Luccino. The information in the column was widely thought to have originated from Lucchino and may have contributed to Epstein breaking off negotiations and resigning his position as General Manager.

Jon Lester cancer story

In August 2006, Massarotti received some criticism for publishing a column detailing rumors that Red Sox pitcher Jon Lester was being tested for cancer. In fact, the rumors turned out to be true and Lester went on to be treated for a rare form of non-Hodgkins lymphoma.

• A Tale of Two Cities: The 2004 Yankees-Red Sox Rivalry and the War for the Pennant, ISBN 1-59-228704-2, co-author John Harper, sportswriter for the New York Daily News

• Big Papi: My Story of Big Dreams and Big Hits, ISBN 0-31-236633-7, co-author David Ortiz, Professional Baseball Player for the Boston Red Sox