Mularkey is undergoing tests at nearby Baptist Medical Center and might be kept overnight, according to a team spokesman.
The Jaguars' first-year coach was in his office early Monday when he began to feel ill. Mularkey made his way to the training room and found a team trainer, who escorted him to the hospital.
"We expect Coach Mularkey to be back at work tomorrow," the team spokesman informed reporters.
Assistant head coach and defensive coordinator Mel Tucker is scheduled to replace Mularkey at Monday's 2 p.m. ET news conference.