Flyhalf Patrick Fa'apale kicked 13 points for Samoa as the hosts held off a bruising second half performance from Tonga for a 30-10 victory in the Pacific Nations Cup.
Samoa had raced to a 23-3 lead at halftime, with 17 points being scored when Tongan winger Otulea Katoa was sinbinned, but found themselves under extreme pressure from the visitors' forwards after the break.
Replacement Danny Tusitala, however, pounced on a loose ball in the 78th minute to seal the game for Samoa, who were in danger of throwing the match away following a poor second half.
Fa'apale slotted three penalties and two conversions for Samoa, who had a man advantage twice in the match with Katoa and fullback David Halaifonua yellow carded.
Samoa replacement prop Viliami Afatia was also given a yellow card late in the second half as Tonga appeared to be getting back in the game.
The hosts were awarded an early penalty try when Katoa was sinbinned by referee Pascal Gauzere for deliberately knocking down the final pass that would have led to a try.
Lock Fa'atiga Lemalu then scored from a rolling maul while Fa'apale added the conversion.
Tonga scrumhalf Tane Takulua had kicked a penalty in the first half for their only points.
Samoa had the opportunity to seal the game when Halaifonua was sinbinned for a shoulder charge, but they were unable to capitalise and Tonga began to shift the momentum with a powerful scrum.
Replacement lock Opeti Fonua crashed over following an attacking scrum and with Afatia yellow carded with 15 minutes remaining it looked like Tonga could steal victory before Tusitala pounced.
Fiji won their fourth successive Pacific Nations Cup title last week when they beat Samoa 26-16 in Suva. The Fijians beat Tonga 23-18 in the first game of the tournament.
The competition was the first stage of qualifying for the 2019 Rugby World Cup, with the two best teams over 2016 and 2017 automatically advancing to the tournament in Japan. The third-placed team meets a European side in a playoff.