The defendants, all Vietnamese, were convicted of trafficking 440 kilograms (970 pounds) of heroin in Vietnam and China, Vietnam News Agency said.
At the end of a nine-day trial Thursday, the Hanoi People's Court also sentenced seven defendants to life in prison and three others to 20-year jail terms, the report said.
The ring was uncovered in December 2004 when Chinese police arrested alleged ring leader Nguyen Thi Nga in Guangxi province and seized 8.5 kilograms (19 pounds) of heroin, it said.
Based on her confession, police arrested her sister, Nguyen Thi Thom, and 19 others between March and December last year, the report said.
Nga was accused of running the ring's China operations, while Thom ran the Vietnamese operations, it said.
Court officials were not immediately available for comment.
Vietnam has among the world's toughest drug laws. Possession, trade or trafficking of more than 600 grams (1.3 pounds) of heroin or 20 kilograms (44 pounds) of opium are punishable by life in prison or death.
About 100 people are put to death by firing squad each year for drug-related offenses.
The discovery of the submarine has unveiled a few "inconsistencies." For example, how can one explain the fact that the sub was found where it needed to be searched for from the start?