Emergency crews said they were helping to remove about 100 people from the passenger train.
The accident happened about 6pm on Monday 15km from Barcelona, the capital of the northeastern region, rail company FGC said in a statement.
The cargo train carrying potash derailed as it came into the Sant Boi station in northeastern Spain.
It then smashed into the front of the passenger train, which was pulling out of the station, killing the engineer, the FGC said.
ZZ/