The French asset management giant has also agreed a distribution partnership with UniCredit covering Italy, Germany and Austria, it said in a statement.
The acquisition – widely expected since Amundi entered into exclusive talks last week – will bring Amundi’s assets under management to almost €1.3trn, the firm said.
Yves Perrier, Amundi’s chief executive, said: “This acquisition will reinforce Amundi’s industrial model and benefit our clients while creating significant value for our shareholders. Pioneer Investments is a world-class asset manager that has a highly complementary business and geographic profile.”
Amundi’s statement highlighted Pioneer’s expertise in European, US and emerging market equities, as well as multi-asset and US fixed income.
Amundi will seek to distribute its smart beta and exchange-traded funds to Pioneer and UniCredit clients, along with global equity and bond products, alternatives and real assets.
Amundi was the 11th largest asset manager in the world this year, according to IPE’s Top 400 asset management rankings.
Pioneer ranked 63rd.
Following the acquisition, Amundi stands to enter the top 10 biggest asset management firms next year upon completion of the deal.
According to the asset manager’s statement announcing the deal, savings should reach roughly €150m through merging or rationalising investment, IT, administration and back-office services.
A further €30m will be saved through “potential cross selling and other revenue optimisation”.
The transaction will be funded by a combination of Amundi’s existing capital reserves, a rights issue and debt issuance.