Jack Draper opened with an impressive straight-set win over Sebastian Baez at the Adelaide International but fellow Briton Katie Boulter lost.
Draper, 22, comfortably beat the 26th-ranked Baez 6-1 6-3 as he continues his preparations for the Australian Open.
However, British number one Boulter suffered a 6-3 6-4 defeat by Romania's Anna Bogdan in the women's event.
Qualifying for the Australian Open was due to begin on Monday but rain prevented any matches being played.
The Australian Open, the first Grand Slam of the year, starts in Melbourne on 14 January.
Draper, the world number 62, is set to join Boulter, Jodie Burrage, Emma Raducanu, Cameron Norrie, Dan Evans and Andy Murray in the main draw in Melbourne.