Kurt Morath kicked 17 points as Tonga beat Fiji 32-20 in Lautoka on Friday in the teams' final warm-up match before next month's World Cup in New Zealand.
The fly-half's conversion and five penalties helped Tonga avenge a 27-12 defeat by Fiji last weekend.
Vungakoto Lilo, Fetu'u Vainikolo and Alipate Fatafehi scored tries for Tonga, while Fiji's tries were scored by Rupeni Nasiga and Leone Nakarawa.
Fiji play Wales in Hamilton in the final Pool D match on 2 October.
Tonga will play hosts New Zealand in the opening World Cup match in Auckland on 9 September.