This study aimed to investigate the effects of social networking sites (SNS) on strengthening self-protective behaviors after COVID-19 to prevent post-COVID-19 conditions in the working-age population in Thailand. Data were collected through a cross-sectional online survey of 400 working-aged Thais. Multiple regression analysis (MRA) was employed to analyze the data at a 0.05 significance level. The findings revealed that YouTube (beta = .275) and Facebook (beta = .182) positively impact self-protective behaviors while Twitter (beta = .237), Facebook (beta = .198) and Tiktok (beta = .119) influence attitudes towards these behaviors. Additionally, Twitter (beta = .206) and LINE (beta = .145) affect subjective norms. YouTube (beta = .288) and LINE (beta = .165) significantly enhance self-efficacy. This study contributes to the broader understanding of how social networking sites can reinforce self-protective behaviors against long COVID-19 among the working-age population. This study contributes valuable insights into the role of social networking sites in promoting health behaviors after COVID-19. The findings offer practical implications for health communication planning by expanding knowledge on the effectiveness of these platforms. Policymakers, social marketers and health organizations can leverage these insights to design targeted interventions to reduce the risk of COVID-19 and prevent future COVID-19 outbreaks at both national and international levels.