Most psychological research questions address human behaviors and attitudes that occur in various groups and organizational contexts. Yet, the most common unit of analysis in psychology has been the individual. Accounting for group-level factors allows researchers to move beyond intraindividual factors and examine behavior and attitude changes within the group context. To introduce one way to study the group effects, the current article provides a beginner’s guide to conceptual application of the group actor–partner interdependence model (GAPIM) for researchers unfamiliar with the model. The GAPIM is a useful statistical approach to model the interrelation of group norms among the members in group settings and consider research questions that involve examining the effects of group norms or contextual influences on individual outcomes. The current article provides a brief developmental background of GAPIM and discusses conceptual applications of key aspects and the basic structure of GAPIM using case examples. Researchers can consider applying GAPIM in modeling the effects of group norms in psychological research, particularly concerning research questions that benefit from moving beyond intrapersonal processes. (PsycINFO Database Record (c) 2018 APA, all rights reserved)