Karlo Siirala

Partner, Member of the Finnish Bar, LL.M.

I am a strategic legal advisor to private equity firms, institutional investors, corporates, and growth companies on complex M&A and private equity transactions, with a focus on cross-border deals in the Nordic region. My practice spans the full deal lifecycle — buyouts, exits, platform investments, and growth/venture capital investments — across sectors including tech, life sciences, financial services, and industrials. I co-head Castrén & Snellman’s Private Equity service.

I have extensive experience advising on transactions for both private and public companies, private equity sponsors, and venture capital firms, at deal sizes ranging from early-stage investments to large-scale, transformative deals. In addition to my private equity and M&A work, I have played a leading role in some of Finland’s largest growth funding rounds, advising both international investors and leading growth companies on transactions that shape the Nordic technology landscape.

I also advise fund managers and investors on a wide range of matters related to private investment funds, such as fund formation, co-investment and consortium arrangements, fund investments and secondary transactions.

I earned my law degree from the University of Helsinki. In addition, I hold an LLM degree from Columbia Law School, where I was recognised as a James Kent Scholar for outstanding academic achievement. Most of my work is cross-border and I have also gained international experience through my secondment to a leading US law firm.

Latest references

We advise Korona Invest and the other shareholders of Innoflame Oy on the sale of Innoflame to Sponsor Capital. The transaction makes Sponsor Capital the new majority owner of Innoflame. Korona Invest has been a shareholder of Innoflame since 2021 and, together with the other selling shareholders, has over the past five years supported the company’s growth, development and several strategically significant corporate transactions, through which Innoflame has strengthened its position as Finland’s leading product media company. The ownership change is intended to support Innoflame’s next phase of growth, including its ambition to build a significant European product media company with the capability to expand rapidly into new markets. The transaction is conditional to the customary closing conditions such as authority approvals. Innoflame is one of Finland’s leading product media specialists, helping its clients build a unified brand experience by offering the design, sourcing and management of product media as a single integrated service. Korona Invest is a Finnish private equity firm founded in 2006, specialising in buyout and growth investments in domestic small and medium-sized enterprises. It makes both majority and minority investments, structuring each project to suit the company’s growth strategy. 
Case published 27.8.2026
We advised Hopeasalmen Telakka Oy, part of Marina Group, on the acquisitions of Iisiveneily and Porvoon Venekorjaamo. The transactions form part of Marina Group’s expansion into the Finnish marina and boatyard sector, strengthening its position under the Quattro Marine brand. Following the acquisitions, Quattro Marine’s Finnish operations comprise Hopeasalmen Telakka, which operates boatyard facilities in Helsinki’s Mustikkamaa and in Tolkkinen, Porvoo, together with Iisiveneily and Porvoon Venekorjaamo. Marina Group is a Norwegian marina and boatyard consortium owned by the private equity sponsor Norvestor. It has grown rapidly through acquisitions to become the Nordic region’s largest boating services provider, having acquired 24 marinas and boatyards across Norway, Sweden and Finland within roughly a year.
Case published 24.8.2026
We advised Efima Oyj on the sale of its financial management services business to Rantalainen as part of its strategic focus on fully concentrating on the delivery of business applications as well as data and AI solutions. As a result of the transaction, customer contracts related to financial management services and 65 experts working in these services will transfer to Rantalainen. The transaction will be carried out as a transfer of business, and the experts will move to the new owner as existing employees. Efima is a Finnish digital company that supports the sustainable growth of large and mid-sized companies by streamlining their business processes and by creating competitive advantage through the innovative use of artificial intelligence and data. The company has nearly 200 experts based in Helsinki and Tampere.
Case published 12.6.2026
We advised lead investor Ugly Duckling Ventures on the EUR 6.5 million funding round of Skyfora. The round also included Eviny Ventures, LUMO Labs and EIC Fund, alongside non-dilutive funding from Business Finland. The investment will support the commercial scale-up of Skyfora’s weather intelligence solutions, the expansion of partnerships with telecom operators, forecasting providers and meteorological institutions, and the continued growth of the team. Skyfora is a Finnish company developing high-resolution weather data solutions using patented technology that extracts atmospheric data from GNSS receivers embedded in existing infrastructure, such as telecom networks. By unlocking previously untapped data sources, Skyfora enables the next generation of AI-driven weather forecasting and supports improved decision-making across weather-sensitive industries. Ugly Duckling Ventures is a Copenhagen-based venture capital firm focused on early-stage Nordic B2B technology companies, with an emphasis on medtech, resilience tech and business services.
Case published 10.6.2026
castren snellman general atlantic iceye
We advised General Atlantic as the lead investor on ICEYE’s EUR 1 billion series F funding round, valuing the company at over EUR 10 billion. ICEYE raised EUR 450 million (USD 520 million) in a primary Series F funding round led by General Atlantic. Additional investors included Solidium, Tesi, Varma, Ilmarinen, Lifeline Ventures, Nokia, Qatar Investment Authority (QIA) and TCV. Together with a secondary placement, the total fundraising exceeds EUR 1 billion. ICEYE is the world leader in sovereign intelligence from space, providing continuous monitoring capabilities to detect and respond to changes in any location on Earth. The company operates the world’s largest and most advanced Synthetic Aperture Radar satellite constellation. General Atlantic is a leading global investor with more than four and a half decades of experience providing capital and strategic support for over 885 companies throughout its history. As of March 31, 2026, General Atlantic manages approximately USD 126 billion in assets across its investment strategies. We advised General Atlantic on this transaction in collaboration with the international law firm Paul, Weiss, Rifkind, Wharton & Garrison.
Case published 9.6.2026
We advised the NATO Innovation Fund as lead investor on Kelluu’s EUR 15 million Series A funding round, with participation from Keen Venture Partners, Gungnir Capital, and Tesi. Kelluu is a Finnish deep tech company operating the world’s largest autonomous airship fleet. We advised NIF on this transaction alongside global law firm Latham & Watkins.
Case published 17.4.2026
We are acting as legal adviser to Taaleri Plc on its acquisition of a 51 per cent ownership stake in Nordic Science Investments Oy (NSI), marking Taaleri’s expansion into deeptech-driven venture capital. Through the transaction, Taaleri broadens its private equity offering into early-stage venture capital funds as well as the commercialisation and scaling of research-driven innovations. NSI is a Finnish venture capital fund manager operating across the Nordic and Baltic regions, focusing on early-stage investments in research- and science-based technologies. Its portfolio companies develop, among other things, health technologies, life sciences, advanced materials and AI-driven solutions. In addition to providing growth capital, NSI supports spin-out companies with strategic guidance, access to networks and assistance in building teams during the early phases of business development. NSI’s first fund, the EUR 45 million NSI Nordic Science I Ky, was established in 2024 and has to date invested in 22 early-stage companies in Finland, Sweden and the Baltic countries. Taaleri is a specialist in investments, private asset management and non-life insurance, with a strong position in renewable energy, bioindustry and housing investments as well as credit risk insurance. Taaleri has EUR 2.7 billion of assets under management in its private equity funds, co-investments and single-asset vehicles, employs approximately 130 people and is listed on Nasdaq Helsinki. The founders of NSI will continue in their operational roles following the transaction. The completion of the transaction is subject to approval by the FIN-FSA.
Case published 13.4.2026
We advised Aurevia Oy, a portfolio company of French private equity sponsor Mérieux Equity Partners, in a strategic reorganisation that involved splitting Aurevia and its parent companies into two independent groups of companies and reorganisation of its existing debt-financing arrangements. Following the reorganisation, the newly formed Aurevia continues as a leading provider of Contract Research Organization (CRO) and Quality Assurance and Regulatory Affairs (QARA) services, while the newly formed Labquality focuses on delivering External Quality Assessment (EQA) services. Aurevia serves operators in the medical devices, in vitro diagnostics and pharmaceutical sectors. Labquality’s customers include clinical laboratories and social and healthcare organisations. The reorganisation positions Aurevia and Labquality to allocate investments more effectively, accelerate growth within their respective customer segments, and respond to evolving market and client needs. The transaction was implemented through multiple parallel demergers and required comprehensive legal and tax structuring across several jurisdictions. Our team supported Aurevia throughout the planning and implementation phases, covering corporate, tax, employment law, and regulatory matters, as well as the optimisation of each group’s financing structure.
Case published 7.4.2026