 
 
BlackRock’s spot Bitcoin exchange-traded funds (ETFs) have become the asset manager’s top revenue source, according to Cristiano Castro, the director of business development at BlackRock Brazil, surpassing products that have been generating revenue for over two decades.
This is a huge feat for BTC, given the company manages more than 1,400 exchange-traded funds globally and is the world’s largest asset manager with over $13.4 trillion in assets under management.
Speaking at the Blockchain Conference 2025 in São Paulo, Castro called their growth “a big surprise” and said that allocations in BlackRock’s Bitcoin funds, including the U.S.-based iShares Bitcoin Trust (IBIT) and Brazil’s IBIT39, had surged to $100 billion this year.
IBIT, which began trading in January of last year alongside roughly a dozen Bitcoin ETFs, currently has around $70.73 billion in assets under management, according to data source SoSoValue, making it by far the most popular exchange-traded fund to track the BTC price.
“When we launched, we were optimistic,” Castro said, “but we didn’t expect this scale.”
 
IBIT’s net inflows surpassed $52 billion in its first year, far outshining all other ETFs that debuted over the past decade. The Bitcoin fund is also estimated to have generated approximately $245 million in annual fees by October 2025.
A wave of institutional demand following the U.S. regulatory approval of spot BTC funds has largely driven IBIT’s strong growth. BlackRock now owns around 3.9% of Bitcoin’s 21 million supply.
BlackRock IBIT’s Record Exodus In November Is “Perfectly Normal”
Castro’s remarks come on the heels of a rollercoaster month for BlackRock’s US-listed IBIT, which witnessed a staggering $2.34 billion in withdrawals this November. The biggest capital exits occurred mid-month, with the fund shedding approximately $463 million on Nov. 14 and around $523 million exiting on Nov. 18 — extending their outflow streak.
According to Castro, such brutal outflows are expected given how retail investors react to price drawdowns.
“ETFs are very liquid and powerful instruments,” Castro reportedly told local media at the Blockchain Conference. “They exist to let people allocate capital and manage cash flow. What we’ve been seeing is perfectly normal; any asset that starts to experience compression usually has this effect, especially in an instrument that is heavily controlled by retail investors.”
Bitcoin has retreated sharply from its October $126,080 all-time high, trading around $91,331 at press time and testing the conviction of newer ETF entrants who purchased near the highs.