Sebastiano Nessi is a Counsel specializing in international arbitration. He represents clients in international commercial, investment and sports arbitration matters as well as in enforcement and setting-aside proceedings before the Swiss Supreme Court. He has also advised states on the negotiation and drafting of investment treaties, and investors on the (re)structuring of their investments. A Swiss national, Sebastiano sits frequently as an arbitrator (president of the tribunal, sole arbitrator and co-arbitrator).

Sebastiano is ranked as one of the 10 Most Highly Regarded lawyers (Future Leaders) in Europe Middle East, Africa (EMEA) by Who’s Who Legal Arbitration. He is also recognized as a National Leader and comes highly recommended by Who's Who Legal Switzerland and Legal500. According to clients and peers, Sebastiano is "tremendously talented", "brilliant", "very sharp and efficient", and he is lauded for his "great advocacy skills" and his "impressive client management skills" (Who’s Who Legal). Other sources praise him for being "a star advocate" (Who's Who legal Switzerland) and a "strong academic" with "multifold expertise in investment arbitration", "who never misses a single detail" and "is always the first to propose an excellent legal solution" (Legal500), and report that he is "probably the best arbitration counsel of the young generation" (Who’s Who Legal Switzerland). Impressed clients remark that "his deep understanding of issues of damages stand out, which contributes a lot to each and every case" (Legal500). He is also recognised as "a top person to contact in Europe for complex arbitration matters" (Who’s Who Legal), and one of the "most promising rising stars in international arbitration" (40 under 40 / LMG Expert Guide). Sebastiano is a Fellow of the Chartered Institute of Arbitrators in London.