The Fijians dominated South Africa 22-0 in the final, helped by two tries from Kalione Nasoko.
Fiji has now won five of the last six tournaments in Hong Kong.
Captain Osea Kolinisau acknowledged the successful history but told World Rugby it didn't play a big part in their build-up this week.
"We weren't focusing on doing it three times," Kolinisau said.
"We said that we were going to take it as if we were searching for [our] first title in the series and I am glad that everybody was up to par and everybody did their job."
Kolinisau said playing at the Hong Kong Sevens was a childhood dream for most Fijians so winning the tournament was extra special.
"Hong Kong seems like a home away from home and we watch a lot of our idols play here," he said.
"It's always the dream of every young Fijian to one day wear the white jersey but [also] wear it in Hong Kong."
Fiji have leap-frogged England on the World Series ladder now, with the Blitz Bokke still leading the standings on 145 points followed by Fiji on 122 and England on 113.
Samoa lost in the semi-finals of the shield competition to wales 26-12 meaning the Samoans only win of the Hong Kong tournament was a 22-12 victory of South Korea in pool play.
The Samoans lie in 13th place on the series table.
Singapore hosts the next tournament in the World Series next weekend.
The series qualifiers were also held in Hong Kong with Spain overcoming Germany in the final 12-7, meaning they will take be a series core team next season.
Papua New Guinea had lost in the semi-finals to the victorious Spaniards while Tonga didn't make it out of their pool, falling to both Germany and Uganda.
Photo by: World Rugby - Martin Seras Lima (The Fiji team celebrate a third consecutive Hong Kong title)