The Vanguard S&P 500 ETF had the most inflows.
Exchange-traded funds (ETFs) continue to be a preferred choice among investors as some $82.4 billion flowed into ETFs in May in the U.S, according to research firm ETFGI.
Year-to-date, ETFs have attracted a record $443.3 billion in net inflows in 2025. The previous YTD record through May was set in 2021 when $399.1 billion flowed into ETFs. Last year, roughly $358.2 billion flowed into ETFs through May.
The May inflows mark the 37th consecutive month of ETF net inflows. It also brought the total assets under management in ETFs in the U.S. to a record $11.04 trillion, according to ETFGI. The previous high was set in January of this year at $10.73 trillion.
“The S&P 500 Index rose by 6.29% in May, bringing its year-to-date (YTD) gain to 1.06% in 2025. The Developed Markets ex-U.S. Index increased by 5.12% in May and is up 16.52% YTD. Among developed markets, Austria and the Netherlands led with gains of 11.40% and 9.12%, respectively,” Deborah Fuhr, managing partner, founder, and owner of ETFGI, said.
Fixed income ETFs beat equities
In a somewhat interesting twist, fixed income ETFs gathered more inflows in May than stock or equity ETFs. It’s surprising because stocks had such a strong month in May, with the S&P 500 returning 6.3% in the month. In contrast, the Bloomberg Barclays US Aggregate Bond Index fell 0.72% last month.
Fixed income ETFs generated net inflows of $25.6 billion in May, bringing the YTD total to $93.7 billion. That’s significantly higher than the $58.0 billion in inflows over the same period last year.
Meanwhile, equity ETFs brought in $24.5 billion last month, bringing the YTD total of net inflows to $148.5 billion. That is less than the $160.2 billion in net inflows equity ETFs saw last year through May.
Commodities ETFs saw net outflows of $1.6 billion in May, but they still have net inflows of $14.2 billion YTD. That’s better than the $5.0 billion in net outflows generated in 2024 through May.
Of the $82.4 billion in inflows in May, $33.8 billion went into active ETFs. Year-to-date, active funds have seen $176.7 billion in net inflows, topping last year’s $108.5 billion through May.
The spike in fixed income ETF flows may reflect the notion that investors are still worried about uncertainty in the stock market, despite the bounce back month in May.
Vanguard S&P 500 sees big inflows
The most popular ETF in May was the Vanguard S&P 500 ETF (VOO), which attracted $10.5 billion in inflows. The Vanguard S&P 500 ETF has brought in $65.5 billion in net assets YTD and has $657.3 billion in total assets, making it the world’s largest ETF.
The Invesco QQQ (QQQ) had the second most flows in May, attracting $8.1 billion. The QQQ, which tracks the Nasdaq 100 index, has $10.4 billion in net inflows this year and $334.1 billion in total assets under management.
The third most popular ETF last month was the iShares Bitcoin Trust (IBIT), which generated $5.9 billion in net new assets, bringing the YTD total to $11.3 billion. The iShares Bitcoin Trust already has $69.2 billion in AUM after launching just a year and a half ago.
Fourth on the list is a fixed income fund, the iShares 20+ Year Treasury Bond ETF (TLT), which attracted $3.82 billion in assets in May. This ETF has just $49 million in inflows YTD and total assets of $49.8 billion.
In fifth place is an actively managed ETF, the iShares U.S. Thematic Rotation Active ETF (THRO). This ETF had $3.77 billion in inflows in May and has seen $4.3 billion flow into it YTD. It has about $4.4 billion in total assets.
Sixth is an international ETF, the iShares MSCI EAFE Value ETF (EFV), which saw $3.6 billion in inflows in May. This ETF has $2.3 billion in inflows YTD and $25.4 billion in total AUM.
