US spot Bitcoin ETFs absorbed roughly $3 billion in net inflows over a nine-day buying streak that began September 17, turning year-to-date flows positive and marking the most aggressive stretch of institutional demand since October 2025, according to fund flow data.

The week ending September 25 accounted for approximately $2.4 billion of that total — the largest weekly haul since October 2025, when Bitcoin traded near its all-time high of around $126,000. September 21 stood out as the strongest single day, with nearly $999 million entering the category.

IBIT dominates the leaderboard

BlackRock's iShares Bitcoin Trust (IBIT) captured approximately $1.2 billion in inflows for the week ending September 25, according to flow data. Fidelity's FBTC followed with around $702 million, and ARK 21Shares' ARKB brought in roughly $295 million. Together, the three products accounted for more than 90% of the capital entering the category during that period.

The concentration of inflows in IBIT and FBTC carries informational weight beyond the headline number. IBIT is the category's largest vehicle, and FBTC draws on Fidelity's retail brokerage network and institutional custody infrastructure. When both products attract capital simultaneously, the pattern suggests broad-based allocation across adviser channels and institutional desks rather than a single large directional position.

ARKB rounding out the top three adds a growth-oriented element. Cathie Wood's ARK Invest has positioned itself as one of Bitcoin's most vocal institutional advocates since the products launched.

A reversal from mid-year outflows

The streak reverses what had been a deeply negative year. By July, cumulative 2026 net flows had sunk to approximately negative $5.8 billion. Bitcoin had fallen roughly 34% from its October 2025 peak near $126,000. The September inflows flipped the year-to-date figure to a modest positive of approximately $934 million.

The timing suggests allocators acted on the drawdown. A 34% decline from the October 2025 peak represents the kind of entry point that value-conscious institutional buyers typically wait for — accumulating exposure at $84,000 rather than near all-time highs.

Bitcoin's spot price stabilized in the $83,000 to $87,000 range during the inflow streak, ticking up slightly on a week-over-week basis. Daily inflows tapered somewhat after the September 21 peak, but the streak held positive through at least September 29.

Category fundamentals

Since the products launched in January 2024, US spot Bitcoin ETFs have accumulated more than $57 billion in cumulative net inflows. Total assets under management across the category approached $108 billion by late September.

The operational consequences are straightforward. Sustained positive flows increase the share of Bitcoin supply held in regulated wrapper structures, deepen the role of authorized participants and custodians in market liquidity, and reinforce the position of the largest issuers — BlackRock and Fidelity — in a category where scale compounds advantages in spreads, marketing reach and distribution.

Whether the streak marks a durable shift or a tactical response to the drawdown will become clearer as daily flow data accumulates through the fourth quarter, with the $2.4 billion weekly figure from September now the benchmark against which subsequent institutional demand will be measured.