BlackRock’s bitcoin exchange-traded funds (ETFs) have become the firm’s most profitable product line, according to Cristiano Castro, director of business development at BlackRock Brazil.

These figures are notable given that the firm manages more than 1,400 ETFs globally and is the world’s largest asset manager with more than $13.4 trillion in assets under management.

Speaking at the Blockchain Conference in Sao Paulo Local mediaCastro called the growth “a big surprise” and said the firm’s allocation to bitcoin ETFs, including U.S.-based IBIT and Brazil’s IBIT 39, had approached $100 billion.

“We were optimistic when we launched,” Castro said, “but we didn’t expect this scale. “

The firm’s US-listed spot bitcoin ETF FIBIT, which launched in January 2024, did so in 341 days, making it the fastest in history to reach $70 billion in assets in 341 days. That momentum continues despite recent volatility in bitcoin’s price, with the ETF currently sitting at $70.7 billion in net assets. Sosolo Data

Net inflows exceeded $52 billion in its first year, outpacing all other ETFs launched in the past decade. IBT also generated an estimated $245 million in annual fees by October 2025.

IBT’s rapid growth has been fueled by BlackRock’s global distribution network and a wave of institutional interest following US regulatory approval of spot bitcoin ETFs. It now accounts for more than 3% of the total supply of bitcoin, and is followed by various BTC-linked products from Blackrock, including offshore ETFs.

Castro addressed recent outlays from bitcoin funds, saying such a movement is expected given how retail investors react to falling prices. “ETFs are a very liquid and powerful tool. They are meant to manage the flow of people,” he said.

BlackRock is betting on its own Bitcoin ETF. Its strategic income opportunities portfolio recently increased its stake in IBT by 14%.

Quindisc has reached out to Blackrock but had not heard back at the time of writing.