The Red Sox tweeted: "So how was everyone's Monday?" The tweet went out a minute after a Missouri prosecutor announced a grand jury decided not to indict a white Ferguson police officer in the death of Michael Brown, an unarmed black 18-year-old.
Hundreds of people pounced, accusing the Sox of being out of touch with a seminal national event.
The franchise deleted the tweet immediately. On Tuesday, Red Sox spokeswoman Zineb Curran said the team's "hearts go out to all who are suffering."
Earlier this month, the New England Patriots apologized after sending out a tweet that thanked a follower with a racist Twitter handle.