The acquisition comes after the company received fund shareholder approval from the $16bn (€11.7bn, £9.5bn) Wells Fargo Advantage Dow Jones Target Date Funds.
The company has also received approval to advise a further $5.5bn of GIA’s assets, increasing the total assets within the transaction to $21.5bn.
The new assets now sit under the Legal & General Investment Management (LGIM) branch of the company.
LGIM said the acquisition will provide scale and distribution in the $6trn US defined contribution market, allowing it to build on its liability driven investment and active fixed income capabilities.
It added that, following the acquisition, LGIM’s proforma international assets have increased to $128.3bn .
Chief executive Mark Zinkula said: “I’m delighted the acquisition has been completed and welcome Jim Lauder and his team to LGIM.
“This transaction now means LGIM’s proforma assets exceed $60bn, placing us in an excellent position to grow our define contribution assets in the US markets and accelerate LGIM’s already strong international growth.”