The incident happened before the start of ESPN's broadcast of an interleague game between the Boston Red Sox and Los Angeles Dodgers.
The Boston Globe reported Kruk, 52, was conscious as he was carried out of the booth on a stretcher.
The network released a statement shortly after the incident indicating the former first baseman and outfielder was not in danger.
"John left the booth feeling dizzy and was diagnosed with dehydration," the statement said. "His vital signs are stable and he's in good spirits. We wish him a speedy recovery."
ESPNBoston.com said Kruk was taken to a medical station within the stadium and was later cleared to return to his hotel after being advised to rest and drink fluids.
USA Today and the Los Angeles Times reported the incident was linked to a diabetic condition.
Kruk, who played for the San Diego Padres, Philadelphia Phillies and Chicago White Sox, compiled a .300 career batting average with 100 homers and 592 RBI over 10 major league seasons from 1986-1995.
He was hired as an ESPN baseball analyst in 2004.