The accident happened on a level crossing near the town of Brezno, according to reports. "At the moment I can confirm 10 dead and 20 injured," fire service spokesman Martin Strba told the news agency.
A total of 36 people were on the coach, all from Banovce-nad-Bebravou in western Slovakia, officials say.
The scene of the crash is close to the popular ski resort of Polomka Bucnik.
Slovak news agency TASR said the collision occurred at about 0900 (0800 GMT) on Saturday.
TASR said several of the casualties had serious injuries.
Two people with serious spinal injuries were airlifted to hospital in the town of Banska Bystrica, while others less seriously hurt were taken to hospital in Brezno, according to the www.sme.sk news website.
The TASR report said the train had derailed but its passengers escaped with minor injuries.