Who Owns Costco (COST)? Institutional Ownership Map

Who owns the most Costco?

The largest disclosed Costco holders are the index giants. This is the single most important fact about COST ownership and the one most "who owns Costco" answers get wrong by leading with a hedge fund: the biggest holders are the funds that have to own Costco because it is a large weight in the S&P 500 and the Nasdaq 100.

Values are each filer's reported long position as of its most recent 13F; live figures and the full holder list are on the Costco ownership page. The "as of" column matters: 13F filings arrive asynchronously, so one quarter's largest filer may be a quarter ahead of another's.

The passive core vs the active money

Read COST's holder list as two layers.

The passive core is the top of the table: State Street, Vanguard, Geode, and the index sleeves inside the other large managers. These managers hold Costco in proportion to its index weight. Their quarter-over-quarter moves track fund flows and index rebalancing far more than any view on the stock. When State Street "adds" 0.02% or Geode adds 2.6%, that is mostly index mechanics and new money flowing into total-market and S&P 500 funds, not an analyst turning bullish on warehouse-club margins.

The active money is everyone making a position-sizing decision. That is where the signal lives, and it is mostly further down the list. The standout active long is Parnassus Investments, an active, conviction-driven mutual-fund manager, which added about 2% to its COST stake last quarter. Among the larger percentage adds, Ensign Peak Advisors (the investment arm tied to a large endowment) lifted its position about 22% and NEOS Investment Management added roughly 28%. On the other side, Citadel cut its disclosed long position by about 11%, and the sharpest trims came from quant and active shops: Voloridge Investment Management cut roughly 66%, Man Group about 31%, and Chilton Investment about 15%. None of those is a verdict on the stock by itself, but a screen of who is adding versus trimming, weighted by manager quality, is the actual use of this data. The smart-money leaderboard is the practical starting view.

A note on reading the "biggest add" line honestly: the single largest percentage increase in COST last quarter came from a custodial/brokerage entity (a retail-platform book), which reflects client flows rather than a conviction view. We do not headline that as active buying. The conviction signal is the active managers named above, not the largest raw percentage move.

One nuance worth flagging: hedge funds sometimes express views through options, and 13F reports put and call positions as flagged rows valued against the underlying. A naive aggregator that sums every COST row into a "long book" turns a protective put into a bullish bet. Our data separates option legs from the long-equity book, so a manager's reported COST long is the share position, not a blended notional. (More on that trap: 13F options, puts and calls explained.)

A data-quality footnote: the Vanguard reorg

If you pull COST ownership from raw EDGAR right now, you will see two Vanguard entities reporting Costco: Vanguard Portfolio Management LLC and Vanguard Fiduciary Trust, both newer entities that began filing separately after an internal reorganization. Sum them naively alongside any legacy Vanguard Group line and you double-count billions of dollars of the same shares. This is the kind of identifier and entity-resolution problem that makes institutional ownership data hard to keep clean, and it is exactly what a sourced, deduplicated layer is for. We model the reorg so the combined view does not inflate Vanguard's true position. (Background: 13F amendments and restatements.)

What 13F does and does not tell you about COST

Four limits to keep in mind before treating any "who owns Costco" number as complete:

• It lags up to 45 days. A 13F reports positions as of quarter-end and is due 45 days later, so the picture can be a full quarter stale by the time you read it. COST can move meaningfully in that window.
• It is long-only. 13F covers long positions in 13(f) securities. Short positions, cash, and most derivatives net exposure do not appear. A fund that looks "long COST" on a 13F may be hedged.
• It misses smaller and foreign holders. Only managers with $100M+ in 13(f) securities must file a Form 13F, so retail, smaller funds, and many non-US holders are invisible here.
• Insiders file separately. Costco's own officers and directors report their trades on Form 4 within two business days, a different and faster feed than 13F. See insider activity for COST and the filing-type comparison.

The honest summary: 13F tells you which large institutions disclosed a Costco long position at the last quarter-end and how it changed, not who owns Costco in real time.

How to track Costco ownership as it updates

The durable workflow is to resolve the entity once, pull the holder list, and diff across quarters rather than reading a single filing. With the REST API:

curl -H "Authorization: Bearer YOUR_KEY" \
  "https://arkolith.com/api/v1/stocks/COST"

For an AI agent, the same data is exposed through MCP tools so the assistant can answer "which funds added Costco last quarter" directly, with each figure carrying its source filing and quarter. Start with the MCP quickstart, the 13F data layer, or the live Costco ownership page. Every figure on those surfaces is sourced to its SEC EDGAR accession, which is the point: an ownership claim without a filing date and quarter-end is incomplete.

Frequently asked questions

Who is Costco's largest shareholder?

Among institutional 13F filers, State Street reports the largest Costco position, around $18 billion at its latest filing, followed by Vanguard and Geode at around $11 billion each. All three are index-fund managers holding Costco in line with its weight in major indexes, not active stock-pickers.

How many institutions own Costco?

673 institutional managers disclose a Costco long position in their most recent 13F filings in our dataset, totaling about $72 billion in reported value. That count covers managers with at least $100M in 13(f) securities; it excludes retail holders, smaller funds, and many foreign holders that do not file 13F.

Which hedge funds own Costco?

Several do, but most hold far smaller stakes than the index giants. Among the recent active moves, Citadel trimmed its disclosed long by about 11% while quant and active shops such as Voloridge, Man Group, and Chilton cut harder; active mutual-fund manager Parnassus added. Screen the full list, weighted by manager quality, on the investors leaderboard rather than reading one fund in isolation.

Is Costco mostly owned by index funds?

At the top of the cap table, yes. The largest disclosed holders are index or quasi-index managers (State Street, Vanguard, Geode), whose stakes track index weight and fund flows. The active, conviction-driven positions sit lower in the list and are where quarter-over-quarter changes carry the most signal.

Is 13F ownership data live?

No. A 13F is a quarterly snapshot filed up to 45 days after quarter-end, so Costco's disclosed ownership can be months old by the time it publishes. Use it for institutional positioning and quarter-over-quarter changes, never as a live book.

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Arkolith turns SEC ownership filings into clean, sourced, queryable data. See the live Costco ownership page, connect an agent through the MCP quickstart, or get a key. Not investment advice.