This study examines the determinants of European universities patenting and co-patenting with companies. The analysis takes into account more than 400 universities from 17 countries over the period 2011-2018. We test several determinants of the commercial activity of universities, such as: student enrolment (size), age, public or private nature of the institution, students per academic staff, publications per academic staff (research orientation), non-academic staff per academic staff, funding structure (core and third-party budget) and prior patent activity. We estimate two-part models with zero-inflated negative binomial/zero-inflated beta regressions, which estimate separately the impact of the determinant of patenting (count data/proportion of joint company-university patents) and the probability of no patenting. The results indicate that the main determinants of universities patenting and co-patenting with companies are: size, age, research orientation and funding structure. As for patents per se, the determinants of starting patenting are the same as continuing patenting, while for joint company-university patents, most of the determinants differently affect starting joint-patenting than increasing the proportion of co-patents with companies in all patents.