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Mariel Dimsey
Partner

Dr. Mariel Dimsey

Mariel Dimsey is an international commercial and investment arbitration specialist with extensive experience in providing international services. She has almost 20 years’ experience acting as advisor, advocate, and arbitrator in numerous international arbitrations, including litigation cases, covering a wide range of legal systems and industries. She is also the immediate past Secretary-General of the Hong Kong International Arbitration Centre (“HKIAC”), a major institution in Asia. Prior to joining the HKIAC, Mariel was a Partner at CMS in the Hong Kong office, Co-Head of CMS International Arbitration, and a key lawyer in the firm's litigation and dispute resolution practice.

She has extensive expertise in both common law and civil law disputes, including disputes involving Chinese parties, and has full professional fluency in German. Mariel regularly sits as arbitrator, bringing her insights to cases under the HKIAC, ICC, KCAB, and DIS Rules, as well as in ad hoc disputes. She is on the arbitrator panels of several major institutions and chambers, reflecting her deep experience and expertise.

She is a past co-chair of the HK45 Committee, and a Member of the WILHK Advisory Board. Mariel is consistently ranked in both the regional and global editions of the leading legal directories, demonstrating the high regard in which she is held by clients and peers alike.

Mariel holds a Dr. iur. (summa cum laude) from the University of Basel, an LLM from the University of Cologne, and an LLB/BA (Business German) from the University of Queensland. She is admitted to practice law in Australia and Hong Kong, offering services that meet the highest international standards. Mariel now heads the CMS Hong Kong office, leading its finance and banking sectors, providing resolution strategies, and delivering key insights to clients across the region.

Awards & Recognitions
01
  • Quote
    Listed as "Thought Leaders"
    Lexology Index 2025: Arbitration (formerly Who's Who Legal)
  • Quote
    "Mariel impressively combines her extensive experience as counsel and arbitrator in international arbitration with her institutional insights"
    Lexology Index 2025: Arbitration (formerly Who's Who Legal)
  • Quote
    "She is one of the most experienced arbitration practitioners in Asia"
    Lexology Index 2025: Arbitration (formerly Who's Who Legal)
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    "She is a great practitioner and a pleasure to work with"
    Lexology Index 2025: Arbitration (formerly Who's Who Legal)
  • Quote
    Listed as "Thought Leaders – Mainland China, Hong Kong SAR and Macao SAR"
    Lexology Index 2025: Arbitration (formerly Who's Who Legal)

Relevant experience

  • Personally appointed as expert on Hong Kong arbitration law concerning an HKIAC arbitration between Cayman Islands and Singaporean parties.
  • Representing a European luxury brand in CIETAC HK proceedings against a Hong Kong company arising from a dispute over intellectual property rights, Hong Kong substantive law, Hong Kong seat.
  • Representing a German company in HKIAC arbitration proceedings concerning delays and other breaches arising from a subcontractor relationship, Hong Kong substantive law, Hong Kong seat. 
  • Representing a Hong Kong company in HKIAC arbitration proceedings concerning delays and other breaches arising from a construction project. 
  • Representing an Indian company in HKIAC arbitration proceedings in Hong Kong against a Chinese company arising from a supply contract. 
  • Representing a multinational chemicals company in UNCITRAL ad hoc proceedings in Frankfurt concerning a supply dispute.*
  • Representing a Middle Eastern client in ICC proceedings in Geneva concerning an energy dispute.*
  • Representing a German investor in an ad hoc bilateral investment treaty arbitration in Geneva, Switzerland under public international law against an Asian state.*
  • Representing a German client in ICC proceedings in Singapore under Swiss law concerning obligations under a share purchase agreement.*
  • Representing a Belgian client in ICC proceedings in Germany under German law in a dispute arising out of a corporate restructuring transaction.*
  • Representing a German corporation in ICC proceedings in Switzerland under U.S. and German law arising out of an intellectual property dispute.*
  • Representing an Italian company in CAM proceedings in Italy under Italian law arising out of an advisory dispute.*
  • German corporation in relation to bilateral investment treaty claims against an Asian state in connection with a construction project.*
  • Asian state on investment protection and arbitration.*
  • German corporation on the availability of investment protection for EPC contracts.*
  • German corporation in relation to bilateral investment treaty claims against a Middle Eastern state in connection with water utilities.*
  • German corporation in relation to investment and contract law claims against various parties in connection with an infrastructure project in Sub-Saharan Africa.*
  • German client in relation to enforcement of an arbitral award against a sovereign state in several jurisdictions.*
  • Belgian client in relation to enforcement of trademark rights in several jurisdictions pursuant to findings in an arbitral award.*
  • Danish citizen in relation to enforcement of an arbitral award in Germany.*
  • U.S. technology company on FCPA and UK Bribery Act compliance concerning a local subsidiary, including conducting a comprehensive internal investigation.*
  • Assisting on achieving global antitrust clearance of a multibillion dollar, three-part transaction between two global pharmaceutical companies.*
  • Advising on anti-trust issues with respect to a large-scale European Commission investigation into price fixing in the automobile industry.*

    *Experience gained prior to joining CMS Hong Kong

Education

  • Solicitor, High Court of Hong Kong, 2017
  • Dr. iur., University of Basel, 2007
  • Lawyer, Supreme Court of New South Wales, Australia, 2006
  • LL.M., University of Cologne, 2005
  • LL.B., University of Queensland, 2003
  • B.A., University of Queensland, 2000