Nielsen SoundScan said Wednesday the song sold 19,000 tracks this week. It sold 2,800 tracks the previous week and 1.75 million tracks to date.
The crowd-pleasing song is a staple of Boston Red Sox games. It makes no specific mention of Boston or the Red Sox, but the team started playing it regularly at Fenway Park more than a decade ago and fans took to it.
The New York Yankees, Toronto Raptors and other professional sports teams have also played the song at games in the days after last week's deadly blasts.
Diamond released "Sweet Caroline" in 1969. It is addressed to Caroline Kennedy.
Pictures from the Boston Marathon bombings (The Associated Press contributed to this report)