Sales from Diamond's song are up by 597%, Nielsen SoundScan said on Wednesday.
Diamond's representative said the singer will donate the recent sales to marathon bombing victims.
Sweet Caroline 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 also have played the song at games in the days after the deadly blasts on 15 April.
Diamond released Sweet Caroline in 1969. The song was inspired by Caroline Kennedy's name.