Flat Capital is a publicly traded family office based in Stockholm, Sweden, founded in 2013 by Nina and Sebastian Siemiatkowski. It invests long-term capital in entrepreneur-led companies globally, with notable positions in OpenAI, SpaceX, Klarna, DeepL, and Figma, operating with a flat cost structure of no fees and no carry.
Deal activity decreased year-over-year (2 deals in the last 12 months vs 3 prior). Average disclosed round size is $61.2M (across 6 rounds with reported amounts).
Portfolio
8
Fund Size
—
Top Stage
Series B
Last 12 Mo
2
Team
SS
Sebastian Siemiatkowski
Partner
Portfolio Breakdown
Stage Distribution
Sector Distribution
Investment Activity
DealsAvg Round Size
Portfolio
9 investments
| Company | Round | Amount | Date |
|---|---|---|---|
 Pixelgen | Series B | $15.5M | Aug 2026 |
 Alpaca | Series D | — | Jan 2026 |
| DDefensor | Unknown | — | Aug 2025 |
| Pixelgen | Series B | $15.5M | Jun 2025 |
 Nexos.ai | Seed | $8M | Jan 2025 |
| AAlpaca Markets | Series C | $150M | — |
| HHemla | Unknown | — | — |
| AAlpacaDB, Inc. | Series D | $150M | — |
 Oden Technologies | Series B | $28.5M | — |
Top Co-Investors
MUFG Innovation Partners3 shared
Opera Tech Ventures3 shared
Unbound3 shared
DRW Venture Capital3 shared
Kraken Ventures2 shared
Peak XV Partners2 shared
Elefund2 shared
Diagram2 shared
Portage Ventures2 shared
Horizons Ventures2 shared
Social Leverage2 shared
Industrifonden2 shared
Aster Capital1 shared
Earlybird Venture Capital1 shared
Endeavor1 shared
General Catalyst1 shared
Y Combinator1 shared
Thrive Capital1 shared
DAG Ventures1 shared
Creandum1 shared
Last updated: 20 October 2026