More than 138,000 people watched Armstrong return from three years of retirement and begin a campaign to win his eighth Tour de France title.
The Austin cycling great stayed well back in a tight field throughout Sunday's race on a winding circuit around leafy Rymill Park, following team instructions to avoid any chance of crashing.
Armstrong will compete in the six-day Tour Down Under, which starts Tuesday. The criterium does not count toward Tour overall standings.
"That was fun," the 37-year-old Armstong said. "It felt good. I've been training a lot for this comeback and this race. It's good the first day is over and now I can get into the racing."
Australia's Robbie McEwen -- a winner of 12 stages in the Tour de France -- won the race for the Russian Team Katusha ahead of Willem Stroetinga of the Netherlands and fellow Australian Graeme Brown.
Armstrong was ushered to the front of the field for the start of the race with another Tour de France winner, Oscar Perero of Spain, defending Tour Down Under champion Andre Greipel of Germany and Australian Stuart O'Grady.
The seven-time Tour de France winner quickly settled in the middle of the peleton, avoiding any possibility of pileups on the tight corners of the 1-mile circuit.
"I think the last time I did that fast a race was back in probably 1990," Armstrong said. "It's fun to get back into it. I found it a bit safer and easier in the back.
"There was a lot of anxiety before today but it was good for the first day."
Johan Brunel, the head of Armstrong's Astana team, was more effusive about the significance of the legendary racer's comeback ride.
"It's a special day," he said. "There's been a lot of talk since August about his comeback and finally it's a fact, so it's a very special moment.
"The instructions were for Lance and the whole team not to concentrate too much about the race but just to get through it. For him it's an important moment to finally put that race number on his back and he's a racer again."