US spot crypto ETF flows diverged again last week.
In the week ended Sept. 18, US spot Bitcoin exchange-traded funds recorded a net inflow of about $6.2 million. The figure stayed positive, but only barely, and only after a sharp recovery on the final trading day of the week. Spot Ethereum ETFs, by contrast, saw about $140 million in net outflows, ending a four-week stretch of positive inflows.
The split in flows did not fully carry over into price action. As of the Asian session on Sept. 21, Bitcoin had moved back above $81,000, while Ethereum also recovered to above $2,600. The report said the latest ETF flow changes look more like short-term institutional position adjustments than a one-way bet on the fundamentals of BTC or ETH.
Bitcoin ETFs finished positive only after a Friday rebound
According to data compiled by SoSoValue, US spot Bitcoin ETFs posted a combined net inflow of about $6.2 million for the week ended Sept. 18.
The weekly total looked calm on the surface, but the daily breakdown told a much more unstable story. Bitcoin ETFs brought in about $160 million on Monday, then swung to roughly $450.3 million in net outflows on Tuesday and another $296 million in outflows on Wednesday. After about $159.5 million returned on Thursday, the weekly running total was still sitting at around $427 million in net outflows.
The turnaround came on Friday, when spot Bitcoin ETFs drew about $433 million in a single day. That was the largest one-day inflow since Sept. 3 and was enough to push the full week back into positive territory. Without that late support, Bitcoin ETFs would likely have posted a second straight week of net outflows. In the prior week, the products had already lost about $462.7 million.
Most of the rebound was concentrated in large funds
At the fund level, the recovery was highly concentrated in a small number of major products.
Fidelity’s FBTC pulled in about $310.7 million on Friday alone, accounting for roughly 70% of the day’s total $433 million inflow. BlackRock’s IBIT added another $108.4 million that same day.
For the full week, IBIT recorded about $120.7 million in net inflows and FBTC took in about $79.9 million. Other Bitcoin ETFs, however, saw combined outflows of about $194.4 million. The report said that points to a market where institutions are not adding exposure across the board. Capital appears to be moving back into the largest and most liquid products instead.
As of Sept. 18, spot Bitcoin ETFs had accumulated about $55.16 billion in net inflows since launch, with total net assets at about $102.53 billion. Looking only at 2026, though, Bitcoin ETFs were still showing about $1.45 billion in net outflows year to date.
Ethereum ETFs broke their four-week inflow run
Ethereum ETFs saw a clearer reversal.
US spot Ethereum ETFs posted about $140 million in net outflows for the week, officially ending a four-week inflow streak. Over those four weeks, the products had attracted about $1.94 billion, so the latest move was described as the first more visible funding correction since mid-August.
The pressure was concentrated between Tuesday and Thursday. Across those three trading days, spot Ethereum ETFs lost about $404.8 million. Friday brought back $143.8 million in net inflows, but that was not enough to offset the midweek withdrawals.
BlackRock’s ETHA took in about $114.3 million on Friday, yet still posted about $56.1 million in net outflows for the week. Fidelity’s FETH added about $26.2 million on Friday, but still ended the week with about $25.8 million in net outflows.
By Friday, spot Ethereum ETFs had total net assets of about $16.72 billion and cumulative net inflows of about $13.25 billion since launch. Unlike Bitcoin, Ethereum ETFs were still up about $922 million on a year-to-date basis in 2026.
The report noted that if the market is viewed only through last week’s flows, it can look like investors were selling ETH and buying BTC. Over the full year so far, however, Ethereum ETF flows were still stronger than Bitcoin’s.
Two reasons highlighted for the renewed divergence
The report pointed to two factors behind the latest split.
First, Ethereum had already built up a meaningful amount of short-term positioning after four straight weeks of inflows totaling about $1.94 billion. That left it more exposed to portfolio rebalancing when macro markets again had to contend with interest rates, energy prices, and volatility across risk assets.
Bitcoin looked different. Bitcoin ETFs had just seen about $463 million in outflows the previous week, and large redemptions also hit in the middle of the latest week. Friday’s rebound therefore looked more like renewed exposure being added after a recovery in price and an improvement in broader risk sentiment.
Second was liquidity. For large institutions, the scale and trading depth of Bitcoin ETFs still far exceed those of Ethereum ETFs. As of Sept. 18, Bitcoin ETFs held about $102.5 billion in net assets, more than six times the roughly $16.7 billion held by Ethereum ETFs.
In that setting, some asset managers may prefer to adjust crypto exposure through Bitcoin ETFs first rather than split allocations evenly across BTC and ETH. The report said that should not be read as outright bearishness on ETH, but as a liquidity-first approach within portfolio allocation.
ETH outflows did not translate into immediate price weakness
One of the more notable details was that Ethereum prices rebounded even as ETFs posted net outflows for the week.
During the Asian session on Sept. 21, Bitcoin traded above $81,000 and was up less than 1% over 24 hours. Ethereum rose about 2% to 3% and moved back above $2,600. Real-time quotes at one point showed Bitcoin near $81,340 and Ethereum near $2,662.
Asian equities and US stock futures also moved higher, while lower oil prices offered some relief on inflation concerns. The MSCI Asia Pacific Index rose close to 1% during Asian trading, and Brent crude fell about 2% to near $101 a barrel.
The report said that helps explain why ETF outflows did not immediately drag Ethereum back to recent lows. ETFs are only one source of market capital. Futures, spot activity, on-chain funds, and global risk appetite can all influence price formation at the same time.
What to watch next
The report said the key issue now is not simply whether Bitcoin ETFs or Ethereum ETFs saw larger inflows over a single week. The bigger shift is that institutional money no longer appears to be increasing crypto exposure across the board the way it did in previous weeks.
Bitcoin ETFs technically stayed positive, but the weekly net inflow was only about $6.2 million, a tiny figure relative to an asset base of more than $100 billion. Ethereum ETFs ended a four-week inflow streak, showing that the stronger allocation demand seen earlier has at least cooled for now.
At the same time, both sides saw clear inflows on Friday: about $433 million for BTC products and about $143.8 million for ETH products. That suggested money had not broadly left the crypto market. It was being redeployed after fast changes in macro conditions and price levels.
The next signal to watch, according to the report, is not the single-day ETF print by itself but whether Friday’s rebound can continue over the next several trading sessions. If Bitcoin ETFs move from a last-day rescue into a multi-day inflow trend, and Ethereum ETFs also return to positive flows, the latest divergence may turn out to be only a short-term rebalancing episode.
If Ethereum swings back to larger outflows while Bitcoin allocations remain concentrated in a few products such as IBIT and FBTC, then a clearer institutional preference may begin to emerge. For now, the data points more to institutions staying in crypto while becoming more selective about where they put money.