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Stephen J. DeCosse (Steve)


(T) +81.3.6800.1819
(F) +81.3.5401.2725


  • University of Wisconsin-Madison (J.D.; Senior Articles Editor, International Law Journal); Princeton University (B.A.)

Bar Admissions

  • Registered Foreign Lawyer in Japan (Daini Tokyo Bar Association) and California

Steve DeCosse focuses on cross-border M&A and investments for strategics, trading houses, and private equity firms. He has handled multiple major inbound and outbound semiconductor M&A deals in recent years, some of which relate to IoT, or the Internet of Things, including various types of sensor technology. He is also active on transport M&A and for sponsors on transportation infrastructure including rail and toll roads. His recent outbound experience extends to energy M&A, metals and mining M&A, grain and commodities M&A, food/agriculture M&A, medical device M&A, and auto parts M&A. He has acted for offshore private equity firms on many inbound Japan M&A deals including in the resort and hospitality sector.

Steve frequently manages anticorruption due diligence for Japanese companies engaged in outbound M&A or projects and sometimes assists large Japanese clients in investigating possible FCPA or other corruption concerns at their offshore operations. He is the editor of Jones Day's annual "Anticorruption Regulation Survey of Select Countries" covering over 40 countries. He is also a member of the Association of International Petroleum Negotiators.

He is currently involved in an Asia-wide pro bono project focusing on human trafficking in six southeast Asian countries.

Honors & Distinctions

  • Cited as a leading lawyer in 2018 in Chambers Asia-Pacific and The Legal 500 Asia Pacific in corporate/M&A, where clients say 'his advice is practical and prompt' and he 'understands exactly what clients need'


English, Japanese
Stephen DeCosse De Cosse Steven Steve