Goteborgs-Posten said the accident involving the 3,200-dwt Rig (built 1989) took place off Laeso early on Thursday.
The smaller boat sank and one crewman fell into the sea.
He was recovered from the water by Swedish authorities, but pronounced dead in hospital.
The master and crew of the cargoship have been questioned.
Rig is operated by Astramar Transport of Riga.
