Public communication campaigns aim to create social change by influencing audiences’ behaviors and thus help nonprofit organizations fulfill their mission. These campaigns, however, often fail to deliver their anticipated impact. Using public relations research as a theoretical lens, this paper's contribution is twofold: first, we develop a typology that classifies the different communication approaches used in public communication campaigns. Based on one of the most prominent public relations theories, the Four Models of Public Relations, we differentiate communication approaches along the dimensions of communication purpose and communication style. Combining these two dimensions in a typology, we identify the following communication approaches: directing, platforming, mobilizing, and involving. We provide numerous real‐life examples of public campaigns for each one. Second, we formulate propositions about these communication approaches’ effectiveness relying on a key concept of public relations research: namely, audience segmentation. Using the transtheoretical model, we show that audiences can be segmented along five “stages of readiness to adopt a promoted behavior.” Conceptualizing behavior change as an iterative, dynamic process that entails stage progresses as well as backdrops, we derive how audiences’ “stage of readiness” relates to the effectiveness of the identified communication approaches.