The 'Ikale Tahi sent coach Toutai Kefu off with a bonus point 45-24 win at the Stade Pierre-Mauroy in Lille on Monday morning, to record their only win at the Rugby World Cup.
Tonga scored seven tries in total in the game against Romania, with winger Solomone Kata claiming a double, one in each half.
They also dedicated the win to their fans and families.
Kefu, who has been at the helm for the Tongans since 2016, told the media at the post-match press conference it was an emotional game for him and the players, adding he was pleased for the team.
He hoped the momentum could continue and that more was done to help Tonga and other Tier-2 teams to get more game time together.
"You could feel it was there. It will probably be more tonight and maybe tomorrow. The boys were pretty focused on really finishing the job," Kefu, the former Wallaby number eight, said.
"I think we don't win much, we win 50 percent, so when you put a programme together, you have got to see what winning is like when you're not winning.
"We have built some capacity around local staff, the boys who have come in have had a really good journey, so those two things mean a lot if you're not winning and they are important.
"I knew if we practised the things we did we were building up to our best performance - and I thought tonight was probably our best performance."
His captain Sonatane Takulua said it was great to send Kefu off with a win.
"I am very happy with the win. Credit to all the boys, our families, our fans. All the brothers that helped Tonga get into the World Cup. Thank you," he said.
"It will mean a lot to our players and especially our coach, finishing up after this World Cup - it is his last game."
Player of the match George Moala, who scored a try and put up a strong performance with some great runs and good defence, was proud to have contributed to the win, having lost three earlier pool matches because of a suspension.
"The boys dug in deep. I am just really happy, great effort from the boys. A really physical game and really happy to finish with a win," he said.
"It was pretty fun. Really happy to be back out there with the boys."