Axa Investment Managers will retain the staff at UK asset manager Framlington, which it bought last week, for at least 12 months.
Nicolas Moreau, chief executive of France's Axa Investment Managers, said none of the 140 staff would lose their jobs before next summer.
He said employees owned 10% of the company, so they stood to make 19.4m (€28.1m) in total from the 194m deal.
Portfolio manager Richard Peirson is set to make 405,000 from his shares as well as long-term incentives and options, based on the most recent shareholder list. Small-cap specialist Roger Whiteoak has the second-highest number of shares among the named portfolio managers and will gain 386,000 from his ordinary shares.
Framlington's assets under management have grown by 187% in less than three years after suffering badly during the bear market. Its revival has been achieved through the abilities of star UK equity managers George Luckcraft, Nigel Thomas and Whiteoak.
Luckcraft's UK equity income fund has doubled in value over the period. Whiteoak's UK smaller companies fund has risen by 126% over the same period.
Moreau said he was confident that the right incentive structure was in place to retain staff.
Luckcraft and Thomas joined Framlington from ABN Amro three years ago in an acrimonious move, which was followed by the Dutch bank merging its UK retail fund management business with UK investment boutique Artemis.
Moreau said Framlington would retain its independent investment style, like its sister subsidiary, Axa Rosenberg, which does not share a back office with its parent.
The rebranded Axa Framlington will sit alongside Axa Rosenberg as part of the group's multi-specialist arm and be distributed across its European and Asian platforms.