Officials say the collision occurred on a train line in Montcada i Reixac, a town just north of Barcelona, at the Montcada station.
Emergency services were alerted to the incident, by a passenger, just before 8am. Fifteen calls were made in total.
A local fire brigade carried out an evacuation of the affected train and firefighters accompanied the injured to health services.
Emergency services for Catalonia said that although three people were taken to medical centres, none of the passengers were considered to be seriously injured.
Some passengers reportedly suffered a broken ankle or bruised nose. Others were given thermal blankets and will be treated a neighbourhood shelter.
Firefighters said that no passengers were trapped.
Local media report that 500 people were travelling in one train and 300 in the other. One passenger told CCMA that the lights turned off and people had “gone flying”.
The Minister of Transport, Raquel Sánchez, and the Minister of Territory, Juli Fernández, have travelled to the scene.
Ms Sánchez told local media: “The important thing is not to make assumptions. We have very capable trains and professionals, but sometimes there are accidents like this and it is best to wait for the results of the investigation that is being carried out.”
President of the Generalitat of Catalonia, Pere Aragonès i Garcia, said: “Following up on the accident in Montcada and Reixac and in contact with [emergency services] to learn about the ... injured, to whom I wish a speedy recovery.
“We need all the explanations from Renfe, Adif and the Spanish government. Improving the service in Catalonia is urgent and cannot be postponed.”
Secretary for the Socialists Party of Catalonia, Salvador Illa Roca, wrote on Twitter: “Very much awaiting the information that continues to reach me from Montcada and Reixac. I wish a speedy recovery to all those injured in this accident.”