Twice Olympic beach volleyball medallist Natalie Cook and new team-mate Nicole Sanderson fought hard as Australia beat China 21-19 17-21 17-15.
Cook has a wealth of experience
Cook, who won gold in Sydney and bronze in Atlanta, used her experience to halt Lu Wang and Whenhui You's comeback.
"Nicole was a bit tight," she said of her partner, who made some errors.
Cook, who has delayed shoulder surgery until after the Games, said it was good to have an early challenge, adding: "I don't like them that tough."
In other Monday games, Bulgarian sisters Tzvetelina and Petia Yanchulova upset 2003 world champions Stephanie Pohl and Okka Rau of Germany 18-21 21-19 15-13.
United States duo Holly McPeak and Elaine Youngs took three sets to beat Canada's Guylaine Dumont and Annie Martin.
But their 21-13 12-21 15-9 victory was enough to ensure they remain in poll position in Group D.
Top US men's pair Dain Blanton and Jeff Nygaard were outblocked by veteran Canadian duo John Child and Mark Heese, who won 21-16 21-10.
The American's must now defeat Swiss duo Patrick Heuscher and Stefan Kobel on Wednesday to have any chance of reaching the next round.
"The pressure may have gotten to the team," Blanton said after the team's second match loss.
"We know what we're capable of doing. We're just not doing it on centre court."
Norway's Vegard Hoidalen and Jorre Kjemperud, who were upset by Sweden in their opening match, found their rhythm to beat Puerto Rico's Ramon Hernandez and Raul Papaleo 18-21 21-19 15-10.
Switzerland's Patrick Heuscher and Stefan Kobel beat Australia's Julien Prosser and Mark Williams 16-21 22-20 15-9.
In the later session, the home crowd saw Greek duo Pavlos Beligratis and Anthanasios Michalopoulos fall 21-14 21-19 to Portugal's Maia and Joao Brenha.
Each team plays three preliminary matches and the top two from each pool advance to the next round of competition along with the four best third-place finishers.