The portal offers internet services such as project collaboration tools to the construction industry. Until now, BuildOnline and rivals such as Asite have only made losses.
Oliver would not reveal details of the group's financial performance but said it was a modest profit at this stage.
"At the beginning of the year we were unprofitable, we were breaking even at the beginning of November and now we have crossed the line to being profitable. It will be small numbers in the early days," he said.
He added that the company was moving into profitability because of its strategy of targeting infrastructure projects such as roads, rail and schools.
"We focused on a sector of the market that is growing rapidly," he said. "If we had focused on the commercial sector we wouldn't have reached profitability so quickly."