Growing by $9.4bn (£7.2bn) in July, assets totalled $539bn and were spread across over two thousand different European-listed exchanged-traded funds (ETF) and products (ETP).
But they have the added flexibility of being traded on exchanges, meaning that they can be bought and sold on an intra-day basis in a similar way to standard stocks and shares.
They are popular for investors looking to gain broad exposure to markets and have historically attracted a lower management fee compared to traditional investment funds.
The increase in July represented the 22nd consecutive month of inflows, but was the best on record during 2016.
"Investor confidence returned during July after the surprising result of June’s Brexit vote," said Deborah Fuhr of ETFGI, who compiled the figures.
ETFs can invest in a variety of asset classes and bond-based ETFs had the largest amount of subscriptions during the month, with $4.8bn of inflows. Equity funds grew by $2.2bn and ETPs attracted net inflows of £2.6bn.
ETPs have one key difference to ETFs in that they are not open-ended funds – they cannot expand and contract share capital – and can invest in a wider-variety of asset classes including commodities, unsecured debt and private partnerships.