"I am OK. Thanks to everyone who has shown their concern," Shockey said in a message posted on his Twitter account. "Don't worry about me. I will be fine."
Saints safety Darren Sharper, who was seen at the hospital where Shockey was being treated, also was with Shockey in the Saints' weight room when the seizure took place.
"It was scary," Sharper said. "We didn't know what was going on."
Sharper said trainers quickly attended to the star tight end, who seemed lucid again after about a minute and was able to walk on his own to an ambulance.
"He said he just felt lightheaded," Sharper recalled.
It was not immediately clear how long Shockey would be hospitalized.
Last summer, before the 2009 training camp began, Shockey had to be hospitalized after passing out from dehydration at a party in Las Vegas.
Shockey had just completed three straight days of offseason training sessions at team headquarters before Thursday's seizure occurred.
The Saints did not officially comment on Shockey's condition, leaving unclear his prospects for getting back on the field when the Saints return to their suburban New Orleans headquarters for minicamp June 4-6.
Shockey was instrumental in helping the Saints win their first Super Bowl last season. He had 48 catches for 569 yards and three touchdowns during the regular season, then in the playoffs had seven catches for 58 yards and two TDs. His final score put the Saints ahead for good in the fourth quarter of their Super Bowl win over the Indianapolis Colts.