This dissertation examines whether and how individuals evaluate risk information on social media holistically to form opinions and make decisions for more and less salient risk issues and seeks to identify strategies to improve risk communication. It bridges competitive framing literature and social norms research to achieve three goals. First, it investigates the extent to which risk issues that are framed in a competitive or complementary manner across multiple social media posts differ in their ability to shape attitudes and behavioral intentions towards different types of risk issues. Second, it explores whether social approval cues implicitly embedded in online comment threads are able to evoke normative perceptions and influence, and impact assessments of strategic risk messages that are framed in a competitive or complementary manner to shape risk judgments and decision making. Third, it ascertains whether the use of dynamic norms, which depict a change in behavioral adoption or approval over time, in strategic risk messages are able to increase message persuasiveness. The findings show that individuals possess a quasi-statistical sense that enable them to scan and accurately interpret social approval towards more and less salient risk behaviors (e.g., getting vaccinated), which influences their attitudes and behavioral intentions. Importantly, social perceptions influence how individuals perceive strategic risk messages framed in a complementary manner, but they had negligible effects when strategic risk messages were framed competitively in the broader social media environment. These findings expand on competitive framing research by delving into the macro-level mechanism (i.e., social norms) underlying competitive and complementary framing effects, which deviates from conventional emphasis on micro-level mechanisms (i.e., individual’s cognition and emotion). The results also expand social norms research by illuminating the mechanisms and boundary conditions underlying dynamic norms. This dissertation offers valuable insights for risk communicators regarding the impact of their strategic risk messaging efforts by demonstrating how social media has transformed public opinion formation and decision making about different types of risk issues. It also highlights the potential of harnessing dynamic norms to encourage less prevalent but pro-social attitudes and behavioral intentions in the risk context.