US spot bitcoin ETFs just had their best week in nearly a year, and the money came in while the price barely moved.
Investors added $2.4 billion to the 12 publicly traded US spot bitcoin ETFs in the week ending September 25, according to SoSoValue data analyzed by The Block. It was the largest weekly inflow since October 2025, and it did something that seemed unlikely two months ago: it pushed the funds back into the green for 2026.
The funds were down about $5.8 billion on the year as recently as July 13. Year-to-date flows turned positive on Tuesday and now stand at roughly $934 million. Cumulative net inflows since launch reached $57.6 billion, with net assets of $108.4 billion as of Friday.
Where the money came from
Most of it arrived on day one. The funds took in $999 million on Monday, their largest daily inflow since October 6, 2025 and the ninth-largest single day since the products launched in January 2024. Inflows then shrank every session: $714.7 million on Tuesday, $347 million on Wednesday, $190.6 million on Thursday and $134.5 million on Friday. Friday still counted, extending the inflow streak to seven straight sessions, a run worth about $3 billion that started on September 17.
BlackRock IBIT led the week with $1.2 billion, its second-largest weekly haul since October 2025. Fidelity FBTC added $701.7 million, its best week since September 8, 2025. Ark and 21Shares ARKB took in $294.7 million, nearly all of it on Monday. Morgan Stanley MSBT drew $203.3 million, its biggest week since launching in April, well above its previous high of $71.1 million set in mid-April.
| Week ending Sept. 25 | Net inflow | Note |
|---|---|---|
| Monday, Sept. 21 | $999.0 million | 9th-largest day since launch |
| Tuesday, Sept. 22 | $714.7 million | |
| Wednesday, Sept. 23 | $347.0 million | |
| Thursday, Sept. 24 | $190.6 million | |
| Friday, Sept. 25 | $134.5 million | 7th straight day of inflows |
| Full week | $2.4 billion | Largest since Oct. 2025 |
The Treasury buyback theory
Analysts tie the timing to the Treasury Department, not to crypto. On August 19, the Treasury said it would increase the maximum size of liquidity-support buybacks of longer-dated nominal securities, doubling operations in the 10-to-20-year and 20-to-30-year sectors from $2 billion to at least $4 billion each. The larger operations took effect September 9 and run through November 4.
Bloomberg ETF analyst Eric Balchunas called it a $4.6 billion wave of cash in a Wednesday post on X and linked it to the buyback plan. Nate Geraci, president of NovaDius Wealth Management, counted $5.3 billion into the funds since the Treasury first announced the buybacks. Monday alone, he wrote, was the ninth-largest inflow day ever.
The connection is loose but not crazy. Larger buybacks in long-dated bonds signal steady Treasury support for the long end of the curve, and bitcoin ETF buyers appear to have read the liquidity picture as supportive. The Treasury itself describes the operations as liquidity support for older securities, not monetary stimulus and not purchases by the Federal Reserve.
There is a prior for this kind of reading. The 2020 and 2021 periods of heavy Treasury and Fed market support coincided with strong inflows into risk assets, including crypto. Whether the analogy holds at a 5 percent policy rate is a different question, and the price tape suggests buyers are hedged on it.
Ether and Solana funds joined in
Spot ether ETFs drew $689.9 million over the same week, reversing a $140 million outflow the week before. BlackRock ETHA led with $326.2 million, followed by Fidelity FETH at $174 million and the Grayscale Ethereum Mini Trust at $100.3 million. Ether funds are now up about $1.6 billion for the year, with $17.8 billion in net assets and $13.9 billion in cumulative inflows since launch.
Solana funds had their own record: $86.7 million on Friday, the largest single day since those products launched in late October 2025, with Bitwise BSOL accounting for $55.7 million of it. The Solana funds drew $188.2 million for the week, second only to their $199.2 million launch week, and hit a record $1.5 billion in combined assets. Spot XRP ETFs added $75.6 million for the week, and the Grayscale Zcash fund briefly topped $1 billion in net assets on Thursday.
Price is not following, yet
The strange part is the tape. Bitcoin traded near $84,000 through the week, roughly flat, and still sits about a third below its $126,198 record from 2025. The macro backdrop explains the gap: the 10-year Treasury yield touched 5.225 percent, its highest since 2007, after the Fed hiked to 3.75 to 4.00 percent on September 16. Futures price 66 to 75 percent odds of another hike in October.
Record ETF bids on one side, a 5 percent risk-free yield pulling on the other, and bitcoin pinned near $84,000 in between. Some analysts argue a close above $90,000 would confirm the next leg; others point out the same resistance capped the market in late August. Both can be right depending on the week.
Trading volume across the bitcoin funds came in at $15 billion for the week, down from $16.2 billion the week before, so the buying has been quiet rather than euphoric. Volume falling while inflows rise points to allocation-style buying rather than short-term trading, the opposite of the pattern from the February and March outflow streaks.
What to watch through November
The buyback program runs through November 4, when the Treasury gives its next quarterly refunding update. If the flows keep pace, the year-to-date cushion will grow from $934 million into something more comfortable. If they stop the moment the program ends, the positive number will look thinner than it does today.
The second date is the October Fed meeting. Another hike would push the risk-free return that competes with bitcoin higher still, and the ETF record so far suggests flows can survive that, but the price cannot fully escape it. The third is ether: if ETH funds keep their streak while BTC volume stays muted, the rotation story gets harder to dismiss.
For now, the week ending September 25 goes down as the clearest institutional vote of confidence in bitcoin funds since the 2025 record run, delivered at a time when the price could not confirm it. That combination, big flows and a flat tape, is rare enough to be worth watching on its own.