It occurred in Pothuhera, about 90 kilometres northeast of Colombo, Sri Lanka's capital.
Police spokesman Ajith Rohana said a train from Colombo travelling to Pallai in the north crashed into a southbound train that was stopped at the station. The cause of the crash is under investigation.
Rohana said four of the injured passengers are in serious condition.
Trains are a popular mode of transport in the island nation, and are generally considered safe.