Bill Ackman Pershing Square: Live Holdings, Concentration, and the Search for Insider Buying (Q1 2026)

Executive summary. Pershing Square's Q1 2026 13F (filed May 15, 2026) discloses 11 positions worth $13.71 billion. Six names — Brookfield, Amazon, Uber, Microsoft, Restaurant Brands, Meta — make up 89.3% of the book. Ackman initiated Microsoft at $2.09B, expanded Amazon 19%, and cut Alphabet by ~95%. Cross-referenced against 13dwatch insider-cluster and insider-intensity feeds on May 26, 2026, zero of the 10 holdings show a Form 4 signal.

Bill Ackman's portfolio is the most-quoted concentrated equity book in U.S. activist investing. The Q1 2026 13F just filed by Pershing Square Capital Management, L.P. (CIK 0001336528) discloses 11 positions, six of which carry the entire book. The remainder are tracking stakes, controlled subsidiaries, or relics of trades being unwound. This is the live data, sourced from the 13dwatch institutional holdings pipeline on May 26, 2026, cross-checked against the SEC EDGAR filing and the 13F.info tracker.

The harder question for an allocator: do any of those positions coincide with Form 4 insider buying? We ran the join. The answer is the answer.

Pershing Square's Q1 2026 portfolio, by the numbers

The 13F-HR for the period ending March 31, 2026, was filed on May 15, 2026, four days before the SEC's 45-day deadline for institutional investment managers with $100 million or more in U.S. equities. Pershing Square Capital Management, L.P. has filed quarterly 13Fs continuously since 2006. The Q1 2026 filing discloses 11 positions and $13,714,299,861 in aggregate reported value.

Source: 13dwatch institutional_holdings table, latest period filter, accession 0001172661-26-002336. The 11th position is a residual Alphabet Class A tracking stake of roughly 32,000 shares.

Six names — Brookfield, Amazon, Uber, Microsoft, Restaurant Brands, Meta — account for 89.28% of the disclosed long book. Add Howard Hughes Holdings and that rises to 97.98%. The bottom three (Seaport Entertainment, Alphabet Class C, Hertz) together sit at roughly 1.95% — these are not investment positions in the conventional sense, as the next section explains.

What changed in Q1 2026

Quiver Quantitative reported on the filing within hours of submission. Three moves dominate the quarter.

Microsoft, new. Pershing Square disclosed 5.65 million shares of Microsoft Corporation valued at $2.09 billion at the quarter end. Ackman, in his commentary, said the stock had declined following earnings and cited Azure cloud business and the firm's AI positioning as the investment thesis. This is the largest new position the fund has opened in any single quarter since the Uber initiation.

Amazon, expanded by 19%. The position rose to 11.45 million shares (from approximately 9.6 million in Q4 2025). Ackman said Pershing bought after the early-April 2026 selloff he referred to as "Liberation Day," a market sell event tied to tariff and tech sentiment.

Alphabet, cut by roughly 95%. Pershing reduced Alphabet Class C holdings from approximately 6.1 million shares (Q4 2025) to roughly 312,000 shares. Class A holdings were cut from approximately 678,000 shares to about 32,000. The combined Alphabet weighting in the book is now under 1%; it was over 8% one quarter earlier.

Aggregate portfolio value fell from $15.53 billion (Q4 2025) to $13.71 billion (Q1 2026), a $1.82 billion decline that reflects both these trims and mark-to-market on the heavy mega-cap weighting.

Concentration: six names is the entire book

Pershing Square's stated investment philosophy is built around eight to twelve large positions. The Q1 2026 disclosure sits at the lower end of that range, weighted heavily toward the top:

• 1 name (BN) = 17.62% of the book
• 3 names = 50.72%
• 6 names = 89.28%
• 7 names = 97.98%
• 10 names ≈ 99.94%

Single-name maximum weight is 17.62%, held by Brookfield Corp. For comparison, a typical large-cap equity mutual fund regulated under the Investment Company Act of 1940 would have to classify a 17.62% single-name weighting as a non-diversified strategy — Pershing Square holds itself out, structurally, as exactly that.

Two of the small positions deserve a footnote.

Howard Hughes Holdings (HHH) — Pershing Square took executive control of HHH after a tender offer that closed in 2025. The 8.70% 13F weight understates the relationship: Ackman is now the controlling shareholder and HHH is run as a Pershing platform. This is a 13F-reported position, but it is structurally a portfolio holding company, not an investment thesis being expressed externally.

Seaport Entertainment (SEG) — SEG is the South Street Seaport spinoff from Howard Hughes, with Bill Ackman as chairman. The 0.79% 13F weight is the post-spin retained stake; Ackman has stated publicly that SEG is run with multi-year patient capital horizons.

Strip out HHH and SEG, and the active equity book becomes seven names totaling 91.27% of the remaining $13.4 billion — eight if you count Alphabet's tracking residual, but the count is the point. Pershing Square does not behave like a fund. It behaves like a private equity firm that happens to disclose its positions every 45 days.

The insider-buying question

Concentrated managers tell allocators a story: when a single name is 15% of your book, you have done more work on it than a diversified manager could possibly do. Allocators trying to evaluate that story often ask the wrong question — "what is Ackman buying?" — instead of the right one: "is anyone closer to the company than he is also buying?"

Form 4 insider transactions are the standard lens for that question. Section 16 of the Securities Exchange Act of 1934 requires directors, officers, and 10% holders to disclose their open-market trades within two business days of execution. The SEC's Form 4 instructions define transaction code "P" as an open-market purchase, which is the cleanest signal: the insider paid market price with their own money. Cluster purchases — three or more distinct insiders buying in a narrow window — historically correlate with positive forward returns (Cohen, Malloy, and Pomorski, 2012, Journal of Finance, among others).

We ran that question against all 10 Pershing Square Q1 2026 positions.

Public signal endpoints used:

• 13dwatch /api/signals/insider-clusters?min_insiders=2&days=180 — surfaced 66 clusters across 62 distinct issuers in the trailing 180 days as of May 26, 2026.
• 13dwatch /api/signals/insider-intensity?min_z=-99 — surfaced 33 issuers above the historical-baseline z-score threshold.

Result for Pershing Square's 10 tickers:

Zero matches. Across every signal threshold we run, none of the names in the Q1 2026 disclosed long book carries a Form 4 cluster or intensity signal. The Restaurant Brands profile page reports three insider transactions in the trailing 365 days — none of them are open-market purchases or open-market sales; the issuer page on 13dwatch shows them as zero-buys, zero-sales (the three rows are non-P, non-S transaction codes — likely option grants, 10b5-1 dispositions, or compensation-related conversions).

The answer to "the three names with insider buying" is, on this snapshot, "zero names with insider buying."

What this means for emerging managers and RIAs

Two reads of this result are wrong. The right read is the third.

Read 1, wrong: "Pershing's book is uninspired." This conflates a backward-looking insider signal with conviction. Insider buying at MSFT, AMZN, BN, META is structurally rare — these are large floats where directors and officers are mostly compensated in restricted stock, not buying in open-market lots. Insider purchases are a small-cap-and-mid-cap phenomenon. The 13dwatch 2018–2026 cluster study found three real activist+insider clusters in 17,592 filings — all in small-cap issuers. The signal is rare and structurally biased to a market-cap segment that Pershing does not fish in.

Read 2, wrong: "Insider data is useless." It is not. It is a noisy but useful filter at the scale where it works — small and mid-cap. Multi-director cluster buys produce above-baseline forward returns in the academic record. The 13dwatch insider_transactions table has 45,440 rows and surfaces meaningful clusters every quarter. Restricting the universe to mega caps simply makes the signal disappear, by construction.

Read 3, right: "Ackman's book is a different signal class." Pershing Square's edge is not insider-overlap. It is two other things: (a) extreme concentration backed by multi-year patient capital — a structure that gives the fund time to be wrong before being right; and (b) friendly activism plus board access — the HHH takeover is the clearest example. Both are signals an allocator can evaluate without insider data. Allocators trying to triangulate Pershing's book against insider buying are using the wrong lens.

For an emerging manager or RIA considering whether to follow Ackman into Microsoft, the question is not "are insiders buying?" It is "do I believe in the same patient-capital, friendly-activism thesis that produces a 17.62% Brookfield weight?" The 13F tells you what he owns. The insider tape, on this set of names, tells you nothing.

Frequently asked questions

What is Bill Ackman's Pershing Square Capital Management?

Pershing Square Capital Management, L.P. is the New York-based hedge fund founded by William Ackman in 2004. It runs a concentrated long-equity strategy of roughly 8–12 positions, supplemented by occasional macro hedges, and publicly listed vehicles including Pershing Square Holdings (PSH.AS) and Pershing Square Tontine Holdings (history). As of the Q1 2026 13F, the disclosed U.S. long-equity book is $13.71 billion across 11 positions (SEC filing).

What is the largest Bill Ackman position right now?

As of Q1 2026, Pershing Square's largest disclosed position is Brookfield Corp (BN) at 59,697,208 shares, $2.42 billion, 17.62% of the long book. Amazon.com is second at 17.39%; Uber Technologies third at 15.71% (13F.info tracker).

Did Bill Ackman buy Microsoft in Q1 2026?

Yes. Pershing Square initiated a new position in Microsoft Corporation (MSFT) during the first quarter of 2026, disclosing 5.65 million shares valued at $2.09 billion at the quarter end. Ackman cited Azure cloud growth, AI positioning, and a post-earnings price decline as the thesis (Quiver Quantitative report, May 15, 2026).

Did Bill Ackman sell Alphabet?

Pershing Square sharply reduced its Alphabet position during Q1 2026. Class C holdings fell from approximately 6.1 million shares to roughly 312,000 — a reduction of about 95%. Class A holdings fell from approximately 678,000 to about 32,000. The combined Alphabet weighting in the disclosed book is now below 1%.

Are any of Pershing Square's stocks seeing insider buying?

As of May 26, 2026, none of the 10 Pershing Square positions disclosed in the Q1 2026 13F appears in the 13dwatch insider-cluster feed (66 active clusters in the 180-day window) or the insider-intensity feed (33 issuers above the z-score threshold). The mega-cap concentration of the book is structurally inconsistent with multi-insider open-market purchase clusters, which are predominantly a small-cap-to-mid-cap phenomenon.

How concentrated is Pershing Square's portfolio?

Six positions account for 89.28% of the disclosed long book; the top three positions are 50.72%. Single-name maximum weight is 17.62% (Brookfield Corp). This level of concentration places the fund well outside the diversification limits that would apply to a 1940-Act-registered mutual fund; Pershing Square's vehicles are structured to permit it.

Methodology and limitations

Data sources: 13dwatch institutional_holdings table (latest-period filter on Pershing Square Capital Management, L.P., CIK 0001336528), /api/signals/insider-clusters (min_insiders=2, days=180), /api/signals/insider-intensity (min_z=-99 to surface all). Quarterly comparison metrics from Quiver Quantitative and 13F.info, cross-checked against the SEC EDGAR 13F-HR filing.

Limitations:

• 13F-HR filings are reported on a 45-day lag. Q1 2026 positions reflect holdings as of March 31, 2026; current positions may differ.
• 13F-HR excludes short positions, non-U.S. equities, cash, and most derivatives. The disclosed long book is not the fund's full exposure.
• "Insider buying" here refers specifically to SEC Form 4 transaction code "P" — open-market purchases by directors, officers, and 10% holders. Other transaction codes (grants, option exercises, 10b5-1 dispositions) are excluded by design.
• Self-filed Form 4s, where the activist filer is also the insider (most relevantly: HHH), are filtered out of cluster signals.

13D Watch publishes original research on activist investing, insider transactions, and institutional positioning. This is research, not investment advice. © 2026 Long Street Consulting, LLC.

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