The deal is its second acquisition in six months since its IPO in March this year, and is part of a broader plan to invest in advisory services for larger organizations.
Ovum CEO Chris Dines said the move will help Orbys expand internationally.
"Our immediate focus will be to expand the sales of Orbys internationally, but ultimately we will seek to develop a range of services for our blue-chip clients," Dines said.
"This acquisition provides excellent synergies and sets the path of establishing Ovum as an advisor at the juncture between vendors and buyers."
Orbys managing director Angela Wyatt said the deal will strengthen its customer service abilities.
"Ovum's geographic reach and commitment to expanding sourcing advisory services internationally will strengthen our ability to service existing and new Orbys clients globally, [while] access to Ovum's research capability [will] widen the scope of services we can offer to clients," Wyatt said.
Orbys generated a turnover of A$9.7 million last year and has a client base which includes Boots, Deutsche Bank and Metropolitan Police Service. It advises clients about sourcing strategies and assists with supplier evaluation and selection, contract negotiation and supplier management.
Ovum Australia, which has about 10 staff locally, was unable to comment.