The side defeated Tonga 8-5 at the Teufaiva Stadium on Saturday.
The Tongans claimed the first round in a thrilling 20-19 victory over Samoa, on 29 November.
The annual Oceania Rugby U20 Trophy which was introduced in 2015, is a key qualification competition with the winner earning a place at the World Rugby Under 20 Trophy in 2023.
Through the support of the Australian Government’s PacificAus Sports program the 2022 tournament increased to a two-match competition.
This is also the first time that Tonga hosted Samoa on home soil.