In a short statement issued this morning, the financial services company said that it expected its sale of Rogge Global Partners, which had £24.1bn of funds under management as at the end of December 2015, to complete in the second quarter of 2016.
Share price for Old Mutual has dropped throughout the day, trading down 2.5 per cent at 157.2p just before 2pm London time.
Under the deal, Allianz will acquire all of the issued share capital in Rogge.
However, financial details about the transaction, including the purchase price, have not been disclosed.
Commenting on the sale, Andreas Utermann, information chief and chief executive elect of Allianz Global Investors, said:
"The two businesses are a natural fit – in terms of both product mix and culture – and we really look forward to working together closely for our clients' mutual interests."
City A.M. has reached out to Old Mutual for further comment but is yet to receive a reply.
Share price for Old Mutual is currently down around 21 per cent on its position three months ago, after being particularly badly knocked in December when the finance minister of South Africa, a country where the company has strong ties, was sacked.
Old Mutual is due to announce its preliminary annual results on 11 March and is set to host its annual general meeting on 12 May.
Last April, Old Mutual appointed Bruce Hemphill as group chief executive, and he officially took up his role in November. Hemphill, who was formerly chief executive of wealth, insurance and non-bank financial services at Standard Bank, succeeded Julian Roberts.