The purpose of this study was to investigate the extent to which professional development predicts principals' instructional leadership in order to identify whether a relationship exists between the duration of principals' participation in distinct professional development activities and their perceived practice of instructional leadership while controlling for several principal and school characteristics. The data employed in this study came from the 2013 teaching and learning international survey, which was conducted by the organisation for economic co-operation and development. Four multivariate regression models with the country-controlled dummy variable were implemented in the analysis of the data. The results indicated that the more principals take part in contemporary professional development activities such as professional networking, mentoring and research activities, the more often they engage in instructional leadership practices. However, no relationship between more traditional types of professional development activities, such as courses, conferences, and observational visits, and principals' instructional leadership, was found. The results have substantial implications for policy-makers and practitioners worldwide, suggesting that any professional development designed to get principles involved in more instructional leadership practices should be based on the contemporary type of professional development activities.