The group was fishing without valid permits in Malaysian waters when they were caught.
They were charged with illegal fishing and using illegal vessels for this activity in Malaysian waters under the Malaysian Fisheries Act 1985.
Some Vietnamese fishermen were charged with the former offense, which can require vessel captains to pay a maximum fine of RM1 million ($238,525) and each vessel crew RM100,000.
Other fishermen were found guilty of using false identities for the fishing vessels.
The specific amount of fines imposed on this group is unknown.
The judge fixed December 14 and 15 for presenting arguments and sentencing.
Another group of 36 Vietnamese fishermen will attend their trial hearing in February and March 2019 after denying similar charges made against them.
All detained Vietnamese fishermen will remain in custody until their hearing.