Investing giant Apollo Global Management is finalizing a deal to buy nearly a 10% stake in Mubadala Capital, the alternative asset manager subsidiary of Abu Dhabi's sovereign wealth fund, Mubadala Investment Company, according to people familiar with the matter who spoke on condition of anonymity.

The deal is expected to be announced later Monday morning, they said. Financial terms were not immediately known.

The transaction is significant on multiple fronts. It further advances Apollo's ambitions in Abu Dhabi, often called the "capital of capital." The firm has spent the past 15 years building key strategic relationships there, with both the country's investment arm and its core leadership.

Apollo already has a multibillion-dollar partnership with Mubadala Investment Company, first established in 2022 and extended two years ago.…