Flows are also sharply down from the money poured in since the start of the year, with March and February seeing $35.8 billion and $49.2 billion in inflows respectively.
"April was a weaker month for ETPs than March, but it continues to be a record year for the popularity of ETPs overall. More money has been put into ETPs so far this year than at the same stage at any other year in the industry's history," head of ETP research at BlackRock, Ursula Marchioni said.
Equity funds overall posted outflows for the month, led by redemptions in U.S. equity funds, which lost $15.5 billion of assets in April after the Fed sounded a cautious tone in its March meeting, causing stocks to rally.
BlackRock said fixed income flows benefitted following the meeting at the expense of equity funds, as investors worried of "stretched valuations" in stocks.
At its March meeting, the U.S. central bank dropped its pledge to be "patient" before raising interest rates, but it also sharply cut its projected path for interest rate increases, as growth and inflation forecasts remain weak.
While investors pulled money from U.S. stocks, European-based ETFs saw decent inflows, with over $5 billion flowing into pan-European equity funds, boosting European-based ETFs past the $500 billion mark for the first time.
"Some 60 percent of the market's growth in 2015 is down to European-domiciled funds. It's a great vote of confidence for the region in a month we celebrated its 15 year anniversary," Marchioni said.
Emerging market equity flows also picked up, seeing $2.5 billion of inflows in April, the "first notable inflows since August 2014", after the Fed cautious tone in March and April, according to BlackRock.