Lawyer Marc Labelle said today his client had the fit overnight and was unable to attend the court proceedings.
Quebec court Judge Carol St-Cyr put off the case until Sept. 2, when the next dates in the trial will be determined.
Thibault is on trial after being charged with fraud and breach of trust in connection with more than $700,000 in alleged improper expenses.
She held the provincial vice-regal post between 1997 and 2007.
St-Cyr ruled this week against a motion filed by Labelle, who argued the case should be dismissed because Thibault benefited from royal immunity.
Thibault took the stand after the ruling.