Kenneth A. Siegel

Kenneth A. Siegel


Amherst College (B.A., 1981)
University of Chicago Law School (J.D., 1986)

Bar Admissions

Japan (Gaikokuho-Jimu-Bengoshi)

Ken is managing partner of the Tokyo office and head of the office’s 50 lawyer M&A team. His practice focuses on the representation of high-technology companies in acquisitions, joint ventures, and strategic alliances.

Ken is consistently ranked as one of the leading U.S. lawyers in Japan. Among other notable accomplishments, he is the only lawyer to be ranked as a “Star Individual” for M&A in Japan (the level above Band 1) by Chambers Global for nine consecutive years (2011 - 2019 editions); he was also ranked in the Band 1 category for the prior decade.

Ken has spent his entire career with MoFo and has practiced in Japan for over 25 years, serving as our Tokyo managing partner for the last 20 years.

Ken has appeared on CNBC and PBS’s Nightly Business Report in their coverage of Japanese legal developments, as well as on the cover of The American Lawyer in its survey of global law firms. He was also recognized by The American Lawyer as “Dealmaker of the Week” for his work on SoftBank’s $21.6 billion acquisition of Sprint, a transaction that was named the Global M&A Deal of the Year by The American Lawyer and also for his work on Hitachi’s $5 billion sale of its hard disk drive business to Western Digital.

Sprint’s $59 billion merger with T-Mobile
Represented SoftBank Group Corp., Sprint’s controlling shareholder, on the landmark merger of Sprint and T-Mobile US, Inc. The total implied enterprise value for Sprint is approximately $59 billion and the aggregate implied enterprise value for the combined company in the all-stock transaction is approximately $146 billion.

SoftBank’s £24.3 billion ($31.4 billion) acquisition of ARM Holdings
Represented SoftBank in its £24.3 billion ($31.4 billion) acquisition of UK-based semiconductor and software design company ARM Holdings. The transaction was the largest-ever cross-border acquisition by a Japanese company (and the largest-ever cash acquisition of a UK company).

SoftBank’s $21.6 billion acquisition of Sprint
Represented SoftBank in its $21.6 billion acquisition of a 78% interest in U.S. wireless operator Sprint. The transaction was the largest U.S. M&A transaction of 2012 and, when announced, the largest cross-border acquisition by a Japanese company (now second to SoftBank’s acquisition of ARM Holdings in 2016).

Toshiba’s $18 billion sale of Toshiba Memory Corporation
Represented Toshiba Corporation in the $18 billion sale of its wholly owned subsidiary Toshiba Memory Corporation to a consortium led by Bain Capital, the largest private equity deal ever undertaken in Asia.

SoftBank’s $7.7 billion investment in Uber
Represented SoftBank in its $7.7 billion primary and secondary investment as part of a $9.3 billion sale of stock by Uber. This is the largest-ever private secondary transaction in the technology space.

Alibaba’s initial public offering on the NYSE
Represented SoftBank, Alibaba’s largest shareholder, in Alibaba’s initial public offering of American Depository Shares on the New York Stock Exchange. The IPO was the largest-ever IPO on the NYSE, initially valuing Alibaba at $168 billion.

Alibaba’s restructuring of its financial services business
Represented SoftBank in the restructuring of Alibaba’s financial services businesses. The restructuring, undertaken in preparation for Alibaba’s IPO, secured and extended Alibaba’s long-term economic participation in Alipay and its broader financial services business.

Alibaba’s $7.6 billion share repurchase of shares from Yahoo
Represented SoftBank in a three-way transaction between SoftBank, Yahoo, and Alibaba, in which Alibaba repurchased half of Yahoo’s shares in the company for $7.6 billion, the parties restated their shareholders agreements, and SoftBank became Alibaba’s largest shareholder, the largest-ever investment/M&A transaction between a Japanese company and Chinese company.

Hitachi’s $4.8 billion sale of Hitachi Global Storage Technologies to Western Digital
Represented Hitachi in the $4.8 billion sale of its hard disk drive subsidiary, Hitachi Global Storage Technologies (HGST), to Western Digital. At the time of sale, HGST had over 40,000 employees worldwide and was one of the world's leading HDD manufacturers.

Hitachi’s air conditioning joint venture with Johnson Controls
Represented Hitachi and Hitachi Appliances on their formation of a global air conditioning joint venture with Johnson Controls, integrating the companies’ market-leading HVAC businesses. Johnson Controls obtained a 60 percent ownership stake in Hitachi Appliances’ more than $2.6 billion global air conditioning business.

TDK Corporation’s $3 billion RF filter joint venture with Qualcomm Incorporated
Represented TDK in the formation of its $3 billion joint venture with Qualcomm to provide industry-leading radio frequency front-end (RFFE) modules and RF filters for mobile devices, drones, robotics, and automotive applications.

Ken Siegel is consistently ranked as one of Japan's leading international attorneys. Among other things, he is recommended as a leading lawyer by Chambers Global, Chambers Asia Pacific, The Legal 500 Asia Pacific, International Financial Law Review (IFLR) and Best Lawyers.

  • The only attorney rated as a "Star Individual" for M&A in Japan (the level above Band 1) by Chambers Global for eight years running (2011 - 2018 editions); ranked in Band 1 for M&A in each of the prior 10 years, the only international attorney to be consistently ranked at this level
  • Ranked as a Leading Individual - Corporate and M&A by The Legal 500 Asia Pacific
  • Ranked as a Market Leader, Mergers and Acquisitions, by IFLR1000
  • Listed in Best Lawyers, Japan, in each year since inception
  • Named Foreign Lawyer of the Year 2018; Tokyo Managing Partner of the Year 2011, 2014 and 2017 (Asian Legal Business (ALB) Japan Law Awards)
  • Named Legal Advisor of the Year (M&A Advisor International – 2013)

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