In a game headlined by clashes in the forward pack, it was Samoa's halves, Anthony Milford and Jarome Luai, who proved the difference, with Milford setting up two of his side's three tries and Luai scoring the other.
It sets up a rematch of the tournament's opening game, which saw England thrash Matt Parish's side 60-6.
The Pacific showdown promised to be the game of the tournament so far, and from the pre-match Sipi Tau and Siva Tau war dances, to the hard-hitting defence and skill on the ball, it didn't disappoint.
After opening the scoring four minutes in, it was Samoa who had the edge through the first 40 minutes and enjoyed the lion's share of possession, but Tonga hung in the game to trail just 12-10 at the break.
After a free-flowing first half which saw plenty of scoring chances created, things tightened up in the second 40, with both sides trading penalty goals before Joseph Suaali'i broke the game open with a run which led to Brian To'o's try.
In the end that was the play that won the game for Samoa, despite a late surge from Tonga which ensured this game thrilled until the very end.
Source: NRL.com
