It is unclear how companies choose intellectual property protection mechanisms (IPPMs) in open innovation and how this choice affects firm performance. Our study addresses these gaps by using a data sample of 415 manufacturing firms from three European countries. The analysis covers eight IPPMs used in open innovation with four types of partners. Findings show that combinations of IPPMs vary according to partner openness. Moreover, companies using all kinds of IPPMs perform better than those relying on informal or semiformal IPPMs.