Skipper Waisea Nacuqu scored two tries in the first half before Samoa fought back from tries to Tuna Tuitama and Motu Opetai to close the contest 12-10 before half time.
The Fijians regrouped in the second half and managed to cross the whitewash twice to Vuiviwa Naduvalo and Manueli Maisamoa to top the pool the Fiji Times reports.
The Ben Gollings-coached side awaits the second team from South Africa and Argentina to meet in the quarter-final tomorrow.
Samoa won their first match against Kenya 31-5 followed by a loss in their second pool match against France 21-19 earlier today.
Photo Manu Samoa FB