A multiparty session formalises a set of concurrent interacting participants. By considering that (a) asynchronous communication models are widely adopted in real-life applications and (b) the possibility for a participant to delegate some interactions to another participant is crucial for the expressivity of concurrent interaction protocols, we propose the first type system for asynchronous multiparty sessions with internal delegation. Our type system enjoys relevant properties: Subject Reduction, Session Fidelity, Lock-freedom and Orphan-message-freedom.