The foundation of the arbitration jurisdiction is the arbitration agreement entered into by the parties to a contract. Usually, only the signatory parties to a contract and the disputes arising from a contract that includes an arbitration clause or to which the arbitration clause relates are the ones that can be submitted to arbitration. This article discusses some of the arguments for extending the arbitration clause in complex arbitrations, that is, in those cases where there are more than two parties, more than two contracts or more than two parties and contracts. Particularly, this paper addresses multiple contract arbitration when the contracts are related. One of the arguments used by the arbitral tribunal for the extension of jurisdiction is the existence of a link between the contracts. Additional arguments include implied consent, participation in the negotiation and performance of a contract and good faith. The article also discusses some of the typical cases of linked contracts in many civil law countries, such as subcontracts, third party beneficiaries and standard terms of contracts, from which arbitral jurisdictions problems may arise. Finally, special attention is given to Article 14 of the 2008 Peruvian Arbitration Law as the first provision in an arbitration law in Latin America that extends the arbitration agreement to non-signatory parties using for this a mixed approach.