Manager Dusty Baker said Griffey became ill on Monday, the team's day off, and wasn't feeling much better. The Reds commemorated his 600th homer before the opener of a series against the Los Angeles Dodgers.
Griffey was on the field with his family while the team showed highlights of his career on the video board. Griffey turned his cap backward and addressed the crowd briefly.
"I just want to thank everybody for coming here," he said. "Thank you."
Fans received a poster and baseball card showing his swing on No. 600. Griffey hit the noteworthy homer last week in Florida, becoming the sixth to reach the mark.
The ceremonies delayed the start of the game by seven minutes.