Ranked by reported Q1 2026 13F market value
Share of total reported institutional value in TNDM held by the largest 10 / 25 filers.
| # | Institution | Shares Held | Market Value | QoQ Change | Ownership % | % of Fund |
|---|---|---|---|---|---|---|
| 1 | BlackRock, Inc. | 10.7M | $204.9M | -4.1% | 15.600% | 0.00% |
| 2 | UBS Group AG | 7.2M | $138.5M | +128.5% | 10.545% | 0.02% |
| 3 | Sessa Capital IM, L.P. | 4.7M | $90.7M | -5.4% | 6.903% | 1.73% |
| 4 | VANGUARD PORTFOLIO MANAGEMENT LLC | 4.0M | $76.6M | β | 5.827% | 0.00% |
| 5 | ArrowMark Colorado Holdings LLC | 3.1M | $59.5M | +7.4% | 4.529% | 1.58% |
| 6 | VANGUARD CAPITAL MANAGEMENT LLC | 3.0M | $58.3M | β | 4.434% | 0.00% |
| 7 | STATE STREET CORP | 2.7M | $51.0M | +0.8% | 3.885% | 0.00% |
| 8 | DRIEHAUS CAPITAL MANAGEMENT LLC | 2.3M | $44.2M | +43.1% | 3.363% | 0.32% |
| 9 | CITADEL ADVISORS LLC | 2.3M | $43.7M | +5.8% | 3.323% | 0.02% |
| 10 | GOLDMAN SACHS GROUP INC | 2.2M | $42.5M | +31.8% | 3.238% | 0.00% |
| 11 | Paradice Investment Management LLC | 2.0M | $39.2M | -1.7% | 2.980% | 7.35% |
| 12 | TWO SIGMA INVESTMENTS, LP | 1.9M | $35.7M | +55.1% | 2.720% | 0.03% |
| 13 | GEODE CAPITAL MANAGEMENT, LLC | 1.7M | $32.2M | +1.8% | 2.451% | 0.00% |
| 14 | JENNISON ASSOCIATES LLC | 1.7M | $31.8M | -17.9% | 2.420% | 0.02% |
| 15 | JACOBS LEVY EQUITY MANAGEMENT, INC | 1.5M | $29.2M | -7.8% | 2.224% | 0.12% |
| 16 | MARSHALL WACE, LLP | 1.4M | $27.7M | +64.8% | 2.105% | 0.03% |
| 17 | MORGAN STANLEY | 1.4M | $26.0M | -34.8% | 1.981% | 0.00% |
| 18 | Freestone Grove Partners LP | 1.3M | $25.5M | -7.8% | 1.942% | 0.18% |
| 19 | First Light Asset Management, LLC | 1.3M | $25.2M | +20.7% | 1.919% | 2.26% |
| 20 | BAILLIE GIFFORD & CO | 1.1M | $20.9M | -4.9% | 1.590% | 0.02% |
| 21 | WELLINGTON MANAGEMENT GROUP LLP | 1.0M | $20.0M | +960.7% | 1.522% | 0.00% |
| 22 | VOYA INVESTMENT MANAGEMENT LLC | 804K | $15.4M | +151.7% | 1.173% | 0.02% |
| 23 | D. E. Shaw & Co., Inc. | 784K | $15.0M | -15.2% | 1.144% | 0.01% |
| 24 | Soleus Capital Management, L.P. | 783K | $15.0M | β | 1.143% | 0.61% |
| 25 | Defilade Capital Management, L.P. | 762K | $14.6M | β | 1.112% | 2.05% |
denotes a marquee investor (Buffett, Burry, ARK, Tiger Global, Pershing Square, Baupost and other widely-followed managers). β% of Fundβ shows how much of that investorβs total 13F portfolio is invested in TNDM β a direct measure of their conviction.
Filings activity in TNDM during Q1 2026, grouped by how each filer changed its position.
Institutions that opened a new TNDM position in Q1 2026
Institutions that fully closed their TNDM position in Q1 2026
8 quarters of 13F filings Β· Ξ columns show change vs prior quarter
| Quarter | Inst. Holders | Ξ Holders | Ownership % | Ξ Ownership | Total 13F Value | Ξ Value |
|---|---|---|---|---|---|---|
| Q1 2026 | 269 | +1.9% | 135.61% | 7.67 pp | $1.54B | 5.4% |
| Q4 2025 | 264 | +7.8% | 143.28% | +65.62 pp | $1.63B | +85% |
| Q3 2025 | 245 | 7.5% | 77.66% | 49.37 pp | $883M | 39% |
| Q2 2025 | 265 | 1.1% | 127.03% | +7.61 pp | $1.45B | +6.4% |
| Q1 2025 | 268 | 14% | 119.42% | 80.57 pp | $1.36B | 53% |
| Q4 2024 | 312 | 3.4% | 199.99% | +0.00 pp | $2.90B | 0.0% |
| Q3 2024 | 323 | +2.5% | 199.99% | +0.00 pp | $2.90B | 0.6% |
| Q2 2024 | 315 | β | 199.99% | β | $2.92B | β |
Source: SEC 13F institutional filings. Ownership % requires market cap data and will show once linked. Ξ columns compare to the immediately prior filed quarter.
Quick answers to the most common questions about buying TNDM stock.
Based on Q1 2026 13F filings, institutional ownership of Tandem Diabetes Care, Inc. stands at 135.6%, held across 269 reporting institutions.
BlackRock, Inc. is the largest reported institutional holder of TNDM, with approximately 10,690,844 shares worth $0.20B as of Q1 2026.
Yes β 2 widely-followed marquee investors appear among the top 25 institutional holders of TNDM, including CITADEL ADVISORS LLC, TWO SIGMA INVESTMENTS, LP.
Our composite Smart Money Score for TNDM is 46 out of 100 (Neutral). It combines net institutional buying activity, ownership shift, marquee investor presence, and holder-count growth.
47 institutions opened new positions in TNDM during Q1 2026, while 42 fully exited. 58 added to existing positions and 163 trimmed.
TNDM institutional ownership fell by 7.67 percentage points quarter-over-quarter, with a net change of +5 holders.
The top 10 institutions account for 52.5% of all reported 13F value in TNDM, and the top 25 account for 76.7%.
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.
Tandem Diabetes Care, Inc. (TNDM) Institutional Ownership