A valid arbitration agreement forms the basis of any arbitration. The parties directly bound by the contract choose to waive their often constitutional right to bring a dispute before the ordinary state courts. Others, such as non-signatory third parties, may not be willing to waive their right to an ordinary court. This leads to the key question of when it is possible to extend an arbitration agreement to third parties. This article examines the legal framework of arbitration in Switzerland, a popular place for international arbitration, form requirements, a landmark decision of the Swiss Federal Supreme Court on this issue, the substantive validity of the agreement relating to third parties, the group of companies doctrine and prerequisites for piercing the corporate veil.