This article theoretically investigates how different ownership structures of patents affect ex ante and ex post incentives for innovation by applying a property rights approach. We explore a model in which two research laboratories invest in R&D to obtain an innovative patent, and after successfully obtaining the patent they determine an ownership structure for the patent. The two parties consider how the determined patent ownership would affect their noncontractible relation-specific investments for commercialisation. We demonstrate that joint ownership of a patent between two parties is optimal. More concretely, if a selfish (altruistic) relation-specific investment is more important than an altruistic (selfish) investment, a joint ownership with no (bilateral) veto is optimal to maximise the joint value. Moreover, when both parties do not commit themselves to joint ownership in advance, they have greater incentive to invest in R&D than committing, even if they understand that joint ownership is desirable ex post.