Bernard Tomic and Matthew Ebden gave Australia a 2-0 lead over South Korea with wins in the opening singles of the Davis Cup Asia Oceania Group 1 second round tie in Brisbane on Friday.
Tomic, 19, was down an early break before reeling off a 7-5, 6-3, 6-3 win over unranked Cho Min-Hyeok.
World No.75 Ebden built on the opening rubber success when he sealed a 6-3, 6-3, 6-4 win over Jeong Suk-Young, ranked 730th.
Wimbledon quarter-finalist Tomic, ranked 36, was entrusted with leading Australia as former world number one Lleyton Hewitt recovers from toe surgery.
Australia will advance to the World Group playoffs in September with victory in Saturday's doubles ahead of Sunday's reverse singles.
Australia have not been in the elite 16-team World Group since 2007.