Tonga secured a first-ever win over Romania in the two sides' final warm-up match ahead of the Rugby World Cup in Bucharest.
A try from scrum-half Sonatane Takulua proved to the difference, with replacement hooker Andrei Radoi only crossing the line late on.
The two sides had only met once previously, at the same venue in 2013, when Tonga were defeated by a single point.
Tonga started brightly, scoring through a penalty try after Romania lost second row Valentin Poparlan to a yellow card.
Kurt Morath's conversion and penalty cancelled out two three-pointers from Romania's Florin Vlaicu to give Tonga a 10-6 half-time lead.
Vlaicu's third penalty cut the gap to just a point before Takulua's try, with two more Morath penalties extending Tonga's advantage to 21-9 before Radoi's late score.
Tonga open their Rugby World Cup campaign against Georgia at Kingsholm, Gloucester on September 19, while Romania start against France at the Olympic Stadium on September 23.
Pens: Vlaicu 3
Tries: Penalty Try, Tukulua
Pens: Morath 3
Romania: 15 Catalin Fercu, 14 Madalin Lemnaru, 13 Paula Kinikinilau, 12 Florin Vlaicu, 11 Adrian Apostol, 10 Danut Dumbrava, 9 Florin Surugiu, 8 Mihai Macovei (c), 7 Viorel Lucaci, 6 Valentin Ursache, 5 Johan Van Heerden, 4 Valentin Poparlan, 3 Paulica Ion, 2 Otar Turashvili, 1 Andrei Ursache.
Replacements: 16 Andrei Radoi, 17 Mihaita Laza, 18 Horatiu Pungea, 19 Marius Antonescu, 20 Daniel Carpo, 21 Valentin Calafeteanu, 22 Michael Wiringi, 23 Ionut Botezatu, 24 Csaba Gal.
Tonga: 15 Telusa Veainu, 14 David Halaifonua, 13 Will Helu, 12 Siale Piutau, 11 Fetu’u Vainikolo, 10 Kurt Morath, 9 Sonatane Takulua, 8 Sione Kalamafoni, 7 Nili Latu, 6 Steve Mafi, 5 Joe Tuineau, 4 Tukulua Lokotui, 3 Halani Aulika, 2 Elvis Taione, 1 Soane Tonga’uiha.
Replacements: 16 Paula Ngauamo, 17 Sona Taumalolo, 18 Sila Puafisi, 19 Hale T Pole, 20 Viliami Ma’afu, 21 Sosefo Ma’ake, 22 Latiume Fosita, 23 Vungakoto Lilo.
Referee: Pascal Gauzère (France)
Assistant Referees: Mathieu Raynal (France), Alexandre Ruiz (France)