Patty Mills did his best to keep the Boomers in touch, finishing with 18 points, but Brazil's big men proved more than Australia could handle.
Brazil had only a 36-35 edge at half-time, but they started the third quarter with a 12-2 spurt capped by back-to-back baskets from Leandrinho Barbosa.
David Andersen tried to lead an Australian rally, scoring eight in a 10-2 run that brought them back within touching distance, 54-49.
Brazil moved back into a 10-point lead, but Australia once again closed to within 67-62 on an Anderson three.
The gap was at four, 73-69 going into the final minute and though Mills missed a three, Joe Ingles made a lay-up to slice the gap further.
The game went into the final few seconds with the Boomers down by two before Marcelinho Huertas scored from the line.
Elsewhere, Nigeria almost squandered a 19-point lead but hung on to beat Tunisia. They dominated the first half and had led 29-10 midway through the second quarter.
But after going in down 31-15 at half-time, Tunisia found their shooting rhythm and Amine Rzig sliced the lead to 33-25 with back-to-back threes.
Mourad El Mabrouk made it a two-point game, 58-56 with 45 seconds left, and Nigeria stretched their lead from the free-throw line and then got two late turnovers to secure the win.