Home / People / Dr. Mariel Dimsey
Portrait of Mariel Dimsey

Dr. Mariel Dimsey

Co-Head of the CMS International Arbitration Group

CMS Hasche Sigle, Hong Kong LLP
57/F, One Island East, 18 Westlands Road Taikoo Place, Quarry Bay
Hong Kong S.A.R.
Hong Kong
Languages English, German

Mariel is an international commercial and investment arbitration specialist based out of the CMS Hong Kong office. She has over 15 years’ experience acting as advisor and advocate in numerous international arbitrations covering a wide range of legal systems and industries. She regularly sits as arbitrator and has significant experience across international arbitration institutions including HKIAC, ICC, KCAB and DIS, and in ad hoc arbitrations pursuant to the UNCITRAL Arbitration Rules and the HKIAC Domestic Rules. She has also acted as party-appointed expert on arbitration matters.

Mariel is an Australian Lawyer and Hong Kong Solicitor (non-practising) and received an LL.M. degree from the University of Cologne and a doctorate in law (Dr. iur.), summa cum laude, from the University of Basel, both in investment arbitration. She started her career in Frankfurt and worked at leading international law firms in Germany and the ICC International Court of Arbitration in Paris, before moving to Hong Kong in 2016. She joined CMS Hong Kong in 2018.

Mariel is ranked in Who’s Who and Legal 500, is a Member and immediate past Co-Chair of the HK45 Committee, and a Vice-Chair of the Committee of Women in Law Hong Kong (WILHK). She publishes and speaks extensively on international arbitration topics. Her native language is English and she is fluent in German.

more less

"A truly international lawyer who bridges the common law and civil law divide masterfully"

Who's Who Legal 2021 – Arbitration

"Mariel comes 'highly recommended' by market sources who consider her 'a very strong advocate' with a 'clear and efficient' approach."

Who's Who Legal 2020

Ranked as one of the five most highly regarded individuals in Asia-Pacific (2019).

Who's Who Legal Arbitration: Future Leaders - Non-partners 2018 & 2019

Ranked for International Arbitration.

Legal 500, 2018 & 2019

Relevant experience

Selected relevant experience includes*

  • The Republic of Armenia in ICSID proceedings commenced by US investors concerning a real estate project.
  • A Chinese SOE in ICC arbitration proceedings in Hong Kong concerning an infrastructure project.
  • A Hong Kong company in HKIAC arbitration proceedings concerning delays and other breaches arising from a construction project.
  • An Indian company in HKIAC arbitration proceedings in Hong Kong against a Chinese company arising from a supply contract.
  • A multinational chemicals company in UNCITRAL ad hoc proceedings in Frankfurt concerning a supply dispute.
  • A Middle Eastern client in ICC proceedings in Geneva concerning an energy dispute.
  • A German investor in an ad hoc bilateral investment treaty arbitration in Geneva, Switzerland under public international law against an Asian state.
  • A German client in ICC proceedings in Singapore under Swiss law concerning obligations under a share purchase agreement.
  • A Belgian client in ICC proceedings in Germany under German law in a dispute arising out of a corporate restructuring transaction.
  • A German corporation in ICC proceedings in Switzerland under U.S. and German law arising out of an intellectual property dispute.
  • An Italian company in CAM proceedings in Italy under Italian law arising out of an advisory dispute.
  • A 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.
  • Sole Arbitrator, ICC Rules, Indian seat, Austrian substantive law, tender dispute, Indian and Austrian parties.
  • Sole Arbitrator, HKIAC Rules, Hong Kong seat, Hong Kong substantive law, supply dispute, Hong Kong and Indonesian parties.
  • Sole Arbitrator, ad hoc, Hong Kong seat, Hong Kong substantive law, payment dispute, English and BVI parties.
  • Sole Arbitrator, ICC Rules, German situs, German substantive law, sales dispute, Bulgarian and German parties.
  • Institution-appointed arbitrator in three-member tribunal, DIS Rules, German situs, German substantive law, supply dispute, German and Indian parties.
  • U.S. technology company on FCPA and UK Bribery Act compliance concerning a local subsidiary, including conducting a comprehensive internal investigation.
  • On achieving global antitrust clearance of a multibillion dollar, three-part transaction between two global pharmaceutical companies.
  • On anti-trust issues with respect to a large-scale European Commission investigation into price fixing in the automobile industry.

* Includes experience gained prior to joining CMS

more less

Memberships & Roles

  • HK45 (Co-chair of the Committee)
  • Women in Law Hong Kong (WILHK), Committee Member
  • ICC Hong Kong, alternate member of Nominations Sub-Committee
  • Swiss Arbitration Association Young Practitioners Group (ASA Below 40)
  • Young Arbitrators Forum of the International Chamber of Commerce (ICC YAF), Former Regional Coordinator Europe
more less


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


In­ter­na­tion­al ar­bit­ra­tion law and rules in Hong Kong
Hong Kong is prob­ably the only city in the world with three lead­ing in­ter­na­tion­al ar­bit­ral in­sti­tu­tions. These are HKI­AC, CI­ETAC (with its CI­ETAC Hong Kong Ar­bit­ra­tion Centre (CI­ETAC HKAC)), and ICC (with...
Fa­cing the fu­ture of in­ter­na­tion­al ar­bit­ra­tion
New pod­cast series ex­plor­ing the evolving chal­lenges and in­nov­a­tions of in­ter­na­tion­al ar­bit­ra­tion by the mem­bers of the CMS In­ter­na­tion­al Ar­bit­ra­tion Group
CMS Dis­putes Talk
In these un­cer­tain times, glob­al busi­nesses in al­most every sec­tor are fa­cing chal­lenges brought about by an un­pre­ced­en­ted op­er­a­tion­al cli­mate. Ac­tions and de­cisions taken dur­ing and im­me­di­ately after...
In­ter­im meas­ures in Main­land Chinese courts in aid of Hong Kong-seated...
On 1 Oc­to­ber 2019, the Ar­range­ment Con­cern­ing Mu­tu­al As­sist­ance in Court-ordered In­ter­im Meas­ures in Aid of Ar­bit­ral Pro­ceed­ings (the “Ar­range­ment”), con­cluded between China’s Su­preme People’s...
Parties to Hong Kong ar­bit­ral pro­ceed­ings can ob­tain in­ter­im meas­ures in...
In­tro­duc­tion In many jur­is­dic­tions, a stand­ard fea­ture of in­ter­na­tion­al ar­bit­ra­tion is that parties to an ar­bit­ra­tion agree­ment can re­quest in­ter­im re­lief from na­tion­al courts in sup­port of en­su­ing...
The Hong Kong In­ter­na­tion­al Ar­bit­ra­tion Centre re­veals its new rules for...
On 1 Novem­ber 2018, the Hong Kong In­ter­na­tion­al Ar­bit­ra­tion Centre’s (here­after, “HKI­AC”) new ar­bit­ra­tion rules (here­after, “2018 Rules”) came in­to ef­fect. The 2018 Rules ap­ply to all ar­bit­ra­tions...