Tomljanovic, who was in the form of her career before being struck down by injury, dug into her reserves, shook off the rust, and came through her first round match at the WTA 125 in Parma, Italy.
Facing local hope Nuria Brancaccio, 292nd in the world but with eight years on her side being aged 23, Tomljanovic won 3-6 6-3 6-1 in one hour, 45 minutes.
Tomljanovic's serve was patchy on Monday - she conceded six double-faults and delivered only one ace, but she showed her experience in the clutch moments. She saved six of 11 break points and won seven of ten on Brancaccio's serve.
Tomljanovic, currently 219th in the world, will now face Renata Zarazua, who was in the top 100 in January but is currently ranked 103.
The Mexican is likely to be a much tougher test, she knocked out seventh seed Viktorija Golubic in the opening round.
Tomljanovic was coming off quarter-finals at Wimbledon and the US Open when her injuries began, a knee problem that eventually required surgery ruling her out of the 2023 Australian Open. While injured she reached No.32 in the world but did not return to action until the US Open in September, only to withdraw with fatigue after one match.
She subsequently won a WTA 125 tournament in Brazil, but after reaching the second round at the Australian Open revealed in February she had undergone surgery to remove non-cancerous uterine tumours.
This was her first match since losing to Hungarian qualifier Dalma Galfi at the Thailand Open at the start of February and first win since beating Petra Martic in the opening round in Melbourne.
Two other Australians are entered in Parma and will play their opening round matches on Tuesday. Current Australian No.1 Daria Saville faces US No.3 seed Ashlyn Krueger while Astra Sharma meets India's Ankita Raina.
