Neither team managed to break through in a defensive-minded first half, which finished 0-0.
In the second half, tries from Santiago Alvarez and Marcos Moneta in quick succession, and an ensuing conversion, put Argentina up 12-0.
Gregoire Arfeuil of France scored a last-minute try but it was too little, too late.
The 12-7 win gave Argentina their third straight title in the World Series, having also come out on top in Perth and Vancouver.
They extended their lead atop the standings to 12 points ahead of Fiji on 88 points entering the Singapore Sevens next week.
While there was a bigger contingent of French fans at the Kai Tak Stadium, their team were unable to repeat their magic when they put away two-time defending champions New Zealand in the quarterfinals on Saturday.
The Kiwis’ women’s team had better luck, defeating archrivals Australia in the final 26-19 for their third straight crown in Hong Kong.
The two sides went back and forth for much of the game, before Jorja Miller scored two tries for New Zealand in the second half to open up a 14-point margin.
Australia’s Mackenzie Davis scored late to add to two tries from teammate Maddison Levi, but their efforts came up short.
The Kiwis now have 96 points in the World Series standings, eight more than Australia ahead of the trip to Singapore for the final stop on the Sevens calendar.
