Rescue teams were at the scene of the accident at Voorschoten, a village near The Hague, the emergency services said, Reuters reported.
A fire department spokesman told Dutch radio that 19 people were taken to hospital. Others were being treated on the spot, the emergency services said.
The front carriage of the night train from Leiden city to The Hague derailed and plowed into a field after the accident, ANP news agency said. The second carriage was on its side and a fire broke out in the rear carriage but was later extinguished, it said.
There were conflicting reports about the cause of the accident.
Earlier reports had said the passenger train had collided with a freight train. Dutch Railways (NS) spokesman Erik Kroeze said a freight train was involved in the accident but could not give details.
Dutch Railways said in a tweet that trains between Leiden and parts of The Hague were canceled due to the accident.