While informal networking has been universally regarded as an important feature of expatriate effectiveness, respective network constructs (yongo, wasta, blat/svyazi, etc.) remain weakly understood when taking expatriates’ ability to connect to local networks into account. Drawing on informal institution and social capital theory, we present informal networks as an important contextual factor in international human resource management (IHRM), relevant to the work of expatriates in particular. We define informal networks by pointing out their distinctive nature in contrast to social networks and developing central themes to guide future research in this area. This is achieved by integrating the informal network context into research themes relevant to the IHRM domain. In this article, seven research themes centering on focal research questions are developed, which, taken together, constitute a future research agenda and expand the typical domain of IHRM research in the informal network context.