Dag Ainsoo

Dag Ainsoo is an Estonian entrepreneur, finance professional, and investor best known as CFO and General Partner of Startup Wise Guys, one of Europe's earliest and most active early-stage accelerator funds. Before becoming a full-time investor, he co-founded and built SmartAD into the largest internet advertising network in the Baltics; the company was ultimately acquired by Modern Times Group AB (MTG), giving Ainsoo first-hand founder and exit experience that informs his investing today. Earlier in his career he worked as a Senior Associate at PricewaterhouseCoopers.

Ainsoo is unusual among investors in that he remains an active operator. Alongside his role at Startup Wise Guys he has held CFO positions at multiple startups — including Click & Grow — and is a co-founder and CFO of Monolith. He is also associated with System Capital as a founder/partner. This blend of finance leadership and operating roles makes him a "numbers" partner within the Startup Wise Guys team, and much of the content he shares publicly focuses on the technical and financial mechanics of running a startup — cash-flow management, runway, and topics such as liquidation preferences.

He is deeply embedded in the Estonian and Baltic venture ecosystem. He serves on the Management Board of the Estonian Private Equity & Venture Capital Association (EstVCA) — where he is in his second term — and has been active with the Estonian Business Angels Network (EstBAN). He is consistently listed among Estonia's most active angel investors.

Ainsoo's education spans Estonia, Finland, and Sweden. He holds a BA and an MA in Business Administration from Tallinn University of Technology (TalTech / Tallinna Tehnikaülikool), studied at Mikkeli Polytechnic in Finland, and earned a master's in Management Consulting from Lund University in Sweden.

• Invests at pre-seed and seed in early-stage B2B startups, primarily in SaaS, fintech, cybersecurity, climate/sustainability, and proptech.
• Personal angel tickets are small and early — roughly €10k–50k — while Startup Wise Guys deploys larger amounts through its accelerator and follow-on funds.
• Values strong technical and financial fundamentals: founders who understand unit economics, cash flow, and disciplined capital use tend to resonate with him.
• Typically participates rather than leads rounds, bringing finance/CFO expertise and accelerator network value alongside capital.
• Prefers founders plugged into (or willing to plug into) the Startup Wise Guys ecosystem of 800+ alumni founders and 500+ mentors.