The privately-owned business operates data centres in Adelaide, Brisbane, Melbourne and Sydney, and claims nearly 300 small-to-medium business clients.
The acquisition would particularly help IBM in the South Australian and Queensland markets, according to David Burns, general manager, IBM Global Services. IBM presently operates seven data centres around the country, but none in those two states.
"Our research with clients tells us that business continuity will become one of their top three priorities over the next 12 months," Burns said.
"Acquiring Classic Blue allows IBM to extend its geographical capabilities, particularly in South Australia and Queensland, strengthen its skills in supporting both IBM and non-IBM platforms, and offer more cost-competitive solutions to meet this growing demand."
Terry Moloney, general manager of IBM information technology services, the division into which Classic Blue will be integrated, said Big Blue planned to take on "as many as possible" of the acquiree's 62 staff, but "there may be a handful where we find we have duplication within IBM".
Classic Blue would continue to operate as a standalone entity for at least 12 months before being integrated into IBM, Moloney said.
Classic Blue itself made an acquisition last year, buying intrusion detection specialist Securix for an undisclosed sum. Classic Blue offers security solutions as well as managed services.
Classic Blue managing director Adrian Bogatez said he had been looking to take the company "to the next step" for some time.
"We had required additional capital and had been looking to expand to new facilities," he said.
"Then in talking to various parties, which included IBM, we decided this was the right approach.
"We'd always made a lot of use of IBM technologies and to a certain extent we aligned our name with IBM."
Classic Blue had been vendor-agnostic however, he said, also being a business partner of Sun Microsystems and Hewlett-Packard.
IBM did not disclose the value of the deal.