We provide a systematic review of the literature on academic engagement from 2011 onwards which was the cutoff year of a previous review in Research Policy. Academic engagement refers to knowledge-related interactions of academic scientists with external organizations, set apart from research, teaching and commercialization. It includes activities such as collaborative research with industry, contract research, consulting and informal ties. We consolidate what is known about the individual, organizational and institutional antecedents of academic engagement, and its consequences for research, commercialization, and society at large. Our findings suggest that individual characteristics associated with academic engagement include being scientifically productive, senior, male, locally trained, and commercially experienced. Academic engagement is also socially conditioned by peer effects and within applied disciplines. In terms of consequences, academic engagement is positively associated with academics' subsequent scientific productivity. We also propose new areas of investigation where evidence is still inconclusive, including individual life cycles effects, the role of organizational context and incentives, cross-national comparison, and the impact of academic engagement on the quality of subsequent research as well as educational, commercial and society-wide impact.