During the January-May period, global net inflows into gold ETFs totaled 623 tonnes, the WGC data showed.
Strong inflows combined with soaring gold prices pushed assets under management in gold ETFs to a new all-time high of 195 billion U.S. dollars.
Gold ETFs listed in North America attracted the biggest inflows in May, with total holdings in the region growing by 102 tonnes to 1,815 tonnes, according to the WGC.
European gold ETFs saw an inflow of 45 tonnes last month as Asian funds, primarily in China, added 4.8 tonnes.
Since its debut in 2003, gold ETFs and similar products have accounted for a significant part of the gold market, with growing acceptance among both institutional and individual investors.
According to the WGC, global gold ETFs have nearly doubled over the past 12 months.