The thrilling final saw Myanmar take the lead twice, but Vietnam equalized both times and the match went into a penalty shootout. Vietnam won it 5-3.
Vietnam had crushed Myanmar 5-2 in their group match.
The tournament was held from December 12 to 18 with Malaysia and Gimhae FC of South Korea completing the lineup.
Vietnam received $12,000 for their efforts, while Myanmar took home $7,000.
Vietnamese players also won the prizes for top scorer and goalkeeper of the tournament.
One player from the U21 team, midfielder Phan Thanh Hau, was recently called up to the senior team by coach Park Hang-seo for the upcoming 2019 AFC Asian Cup in January.