"It’s one big terrible nightmare," Alexandre Galipeau told CBC's Daybreak.
"I have to have confidence. I know it will be hard, it will be long. I have to fight in Czech Republic … to be able to represent myself in court to try and bring back my daughter to Canada, but I cannot not say I’m 100 per cent sure I will see my daughter again."
His daughter, Maria Zabranska, was last seen Monday before her mother, Marcela Zabranska, picked her up from her St-Jean-sur-Richelieu, Que., home.
Galipeau has sole custody, but the child's mother had visitation rights, he said.
Zabranska is believed to have returned to the Czech Republic with Maria in tow, Sûreté du Québec investigators confirmed on Tuesday.
Galipeau said he contacted police Monday night after his calls and texts to Maria's mother went unanswered.
He said he and Zabranska had a court date yesterday for a final judgment in the custody case, which has been working its way through the courts for two years.
"I was scared that if I go back in Czech Republic, I would never be able to come back with my daughter," he said. "I was doing everything possible to fix it here in Canada so everything was right and good in the judgment — so she can’t leave Canada."
Quebec provincial police are working with Czech authorities to locate Maria and her mother and are asking anyone with information to get in touch with them.
The Czech Republic's central authority has said it will recognize the custody order from Canada.