Ranked by reported Q1 2026 13F market value
Share of total reported institutional value in BIIB held by the largest 10 / 25 filers.
| # | Institution | Shares Held | Market Value | QoQ Change | Ownership % | % of Fund |
|---|---|---|---|---|---|---|
| 1 | BlackRock, Inc. | 16.0M | $2.93B | +7.8% | 10.820% | 0.05% |
| 2 | PRIMECAP MANAGEMENT CO/CA/ | 14.8M | $2.71B | 0.0% | 9.996% | 2.13% |
| 3 | FMR LLC | 12.8M | $2.35B | +35.9% | 8.675% | 0.13% |
| 4 | VANGUARD CAPITAL MANAGEMENT LLC | 9.5M | $1.75B | — | 6.460% | 0.04% |
| 5 | STATE STREET CORP | 7.2M | $1.31B | +0.1% | 4.855% | 0.05% |
| 6 | VANGUARD PORTFOLIO MANAGEMENT LLC | 6.5M | $1.20B | — | 4.424% | 0.06% |
| 7 | GEODE CAPITAL MANAGEMENT, LLC | 4.3M | $793.4M | +3.4% | 2.941% | 0.05% |
| 8 | WELLINGTON MANAGEMENT GROUP LLP | 3.0M | $543.0M | -16.6% | 2.006% | 0.10% |
| 9 | MORGAN STANLEY | 2.2M | $398.0M | -6.6% | 1.470% | 0.02% |
| 10 | AQR CAPITAL MANAGEMENT LLC | 1.9M | $346.2M | +25.8% | 1.303% | 0.16% |
| 11 | Invesco Ltd. | 1.7M | $320.0M | +5.4% | 1.182% | 0.05% |
| 12 | Boston Partners | 1.7M | $311.7M | -1.2% | 1.151% | 0.33% |
| 13 | AtlasMark Financial, Inc | 1K | $284.5M | — | 0.001% | 0.03% |
| 14 | NORTHERN TRUST CORP | 1.4M | $265.2M | +0.0% | 0.980% | 0.04% |
| 15 | SUSQUEHANNA INTERNATIONAL GROUP, LLP | 1.4M | $262.9M | -38.1% | 0.971% | 0.03% |
| 16 | UBS ASSET MANAGEMENT AMERICAS INC | 1.4M | $252.5M | -1.0% | 0.933% | 0.05% |
| 17 | Legal & General Group Plc | 1.3M | $247.5M | -7.5% | 0.914% | 0.06% |
| 18 | GOLDMAN SACHS GROUP INC | 1.2M | $215.9M | +1.8% | 0.798% | 0.02% |
| 19 | BANK OF AMERICA CORP /DE/ | 1.2M | $212.0M | +2.4% | 0.783% | 0.02% |
| 20 | CHARLES SCHWAB INVESTMENT MANAGEMENT INC | 1.1M | $210.7M | +0.5% | 0.778% | 0.03% |
| 21 | DIMENSIONAL FUND ADVISORS LP | 1.1M | $197.9M | +12.3% | 0.731% | 0.04% |
| 22 | DEUTSCHE BANK AG\ | 1.1M | $195.0M | +11.5% | 0.721% | 0.06% |
| 23 | Pictet Asset Management Holding SA | 913K | $168.3M | -3.6% | 0.619% | 0.18% |
| 24 | VANGUARD FIDUCIARY TRUST CO | 826K | $151.3M | — | 0.559% | 0.04% |
| 25 | Point72 Asset Management, L.P. | 814K | $149.3M | -78.6% | 0.552% | 0.21% |
denotes a marquee investor (Buffett, Burry, ARK, Tiger Global, Pershing Square, Baupost and other widely-followed managers). “% of Fund” shows how much of that investor’s total 13F portfolio is invested in BIIB — a direct measure of their conviction.
Filings activity in BIIB during Q1 2026, grouped by how each filer changed its position.
8 quarters of 13F filings · Δ columns show change vs prior quarter
| Quarter | Inst. Holders | Δ Holders | Ownership % | Δ Ownership | Total 13F Value | Δ Value |
|---|---|---|---|---|---|---|
| Q1 2026 | 976 | +0.7% | 80.74% | +1.07 pp | $23.85B | +1.3% |
| Q4 2025 | 969 | +11% | 79.67% | +19.71 pp | $23.53B | +33% |
| Q3 2025 | 871 | +3.3% | 59.96% | +5.03 pp | $17.71B | +9.2% |
| Q2 2025 | 843 | 0.8% | 54.93% | 1.12 pp | $16.22B | 2.0% |
| Q1 2025 | 850 | +2.3% | 56.05% | 5.87 pp | $16.55B | 9.5% |
| Q4 2024 | 831 | 5.1% | 61.92% | 13.67 pp | $18.29B | 18% |
| Q3 2024 | 876 | 3.0% | 75.59% | 29.06 pp | $22.32B | 28% |
| Q2 2024 | 903 | — | 104.65% | — | $30.91B | — |
Source: SEC 13F institutional filings. Ownership % requires market cap data and will show once linked. Δ columns compare to the immediately prior filed quarter.
Quick answers to the most common questions about buying BIIB stock.
Based on Q1 2026 13F filings, institutional ownership of Biogen Inc. stands at 80.7%, held across 976 reporting institutions.
BlackRock, Inc. is the largest reported institutional holder of BIIB, with approximately 15,974,601 shares worth $2.93B as of Q1 2026.
Yes — 2 widely-followed marquee investors appear among the top 25 institutional holders of BIIB, including SUSQUEHANNA INTERNATIONAL GROUP, LLP, Point72 Asset Management, L.P..
Our composite Smart Money Score for BIIB is 65 out of 100 (Bullish). It combines net institutional buying activity, ownership shift, marquee investor presence, and holder-count growth.
149 institutions opened new positions in BIIB during Q1 2026, while 142 fully exited. 622 added to existing positions and 197 trimmed.
BIIB institutional ownership rose by 1.07 percentage points quarter-over-quarter, with a net change of +7 holders.
The top 10 institutions account for 60.1% of all reported 13F value in BIIB, and the top 25 account for 74.5%.
All data is sourced from SEC Form 13F filings, which institutional investment managers with at least $100M in assets are required to file each quarter. We process every 13F filing from EDGAR and recompute the aggregates after each cycle. Insider transactions are sourced from Form 4 filings.
Biogen Inc. (BIIB) Institutional Ownership