This dissertation examines the role of compassion and anger in communicating the human health impacts of environmental pollution and how the two emotions contribute to increasing prosocial behavioral intentions. Drawing on literature on discrete emotions, mixed emotions, prosocial behaviors, order effects, and emotional flow, this dissertation investigates the role of compassion and anger in prosocial communication from three different angles. Chapter 2 presents two experiments that study compassion and anger as appeals that augment the persuasiveness of messages. Chapter 3 documents an experiment that examines compassion and anger as a dynamic process that develops and evolves during audience’s message exposure. Chapter 4 reports on an experiment that investigates compassion and anger as incidental cues to and products of messages and examines whether the two functions of emotions work jointly. Overall, this dissertation contributes to the literature in a number of ways. In Chapter 2, it connects victim portrayals with collective action, expands the array of emotions in predicting collective action, and furthers the investigation of collective action in third-party contexts. In Chapter 3, it integrates classic research on order effects with the emerging emotional flow perspective, explores an understudied emotional experience, empathic anger, and provides new insights on the role of emotional intensity in influencing persuasion. In Chapter 4, it explores how incidental and message-induced emotions may or may not interact to influence persuasion and complements existing research on the moderating effect of political ideology regarding environment-related messaging. Practically speaking, this dissertation research offers useful guidance to help researchers and practitioners design more effective messages and communication tools to encourage prosocial behaviors.