This research investigates the influence of Instagram Reels on women’s intentions to adopt menstrual cups (MC) for menstrual hygiene management. MCs offer a sustainable and economical alternative to conventional products, providing personal benefits while addressing broader environmental concerns. However, encouraging adoption remains challenging. Drawing upon the Integrative Model of Behavioral Prediction (IMBP), normative influence, and Social Cognitive Theory (SCT), this study examines how messages of prevalence and demonstration embedded in Instagram Reels shape behavioral intentions through key mediators. A pilot study (n = 125) confirmed the effectiveness of the manipulations. The main experiment (n = 312, U.S.-based biologically female aged 18–45) used a 2x2 between-subjects factorial design manipulating prevalence of MC use (high vs. low) and demonstration format (visual vs. verbal-only). Each Reel featured the same actress explaining MC benefits, varying only in whether she described the product as common or uncommon and whether she demonstrated its use on a puppet model or explained it verbally. Participants viewed one Reel and completed measures of attitudes, descriptive and injunctive norms, self-efficacy, perceived behavioral control (PBC), and behavioral intention to adopt MC. As hypothesized, the high-prevalence condition predicted intentions to adopt MC. Prevalence led to higher descriptive norms, injunctive norms, and self-efficacy, and injunctive norms and self-efficacy also mediated intentions, while descriptive norms did not. The demonstration manipulation showed no direct effect on intentions, though visual demonstration improved attitudes, which mediated intentions. No indirect effects emerged through self-efficacy, PBC, or norms in the demonstration pathway. The prevalence x demonstration interaction was nonsignificant. The findings show that short-form videos can strengthen attitudes, confidence, and perceptions of approval, but are limited in changing control-related beliefs. In line with the IMBP, different message features activated distinct belief pathways, underscoring the need to align message design with specific determinants of intention. From a normative influence perspective, signaling that MC use is widespread also led participants to infer that it is socially supported, underscoring the tendency for descriptive cues to influence injunctive norms. From an SCT perspective, learning that many others use MCs strengthened efficacy more effectively than observing a brief demonstration. Together, these insights highlight the potential and limits of Instagram Reels as tools for promoting menstrual health.This research investigates the influence of Instagram Reels on women’s intentions to adopt menstrual cups (MC) for menstrual hygiene management. MCs offer a sustainable and economical alternative to conventional products, providing personal benefits while addressing broader environmental concerns. However, encouraging adoption remains challenging. Drawing upon the Integrative Model of Behavioral Prediction (IMBP), normative influence, and Social Cognitive Theory (SCT), this study examines how messages of prevalence and demonstration embedded in Instagram Reels shape behavioral intentions through key mediators. A pilot study (n = 125) confirmed the effectiveness of the manipulations. The main experiment (n = 312, U.S.-based biologically female aged 18–45) used a 2x2 between-subjects factorial design manipulating prevalence of MC use (high vs. low) and demonstration format (visual vs. verbal-only). Each Reel featured the same actress explaining MC benefits, varying only in whether she described the product as common or uncommon and whether she demonstrated its use on a puppet model or explained it verbally. Participants viewed one Reel and completed measures of attitudes, descriptive and injunctive norms, self-efficacy, perceived behavioral control (PBC), and behavioral intention to adopt MC. As hypothesized, the high-prevalence condition predicted intentions to adopt MC. Prevalence led to higher descriptive norms, injunctive norms, and self-efficacy, and injunctive norms and self-efficacy also mediated intentions, while descriptive norms did not. The demonstration manipulation showed no direct effect on intentions, though visual demonstration improved attitudes, which mediated intentions. No indirect effects emerged through self-efficacy, PBC, or norms in the demonstration pathway. The prevalence x demonstration interaction was nonsignificant. The findings show that short-form videos can strengthen attitudes, confidence, and perceptions of approval, but are limited in changing control-related beliefs. In line with the IMBP, different message features activated distinct belief pathways, underscoring the need to align message design with specific determinants of intention. From a normative influence perspective, signaling that MC use is widespread also led participants to infer that it is socially supported, underscoring the tendency for descriptive cues to influence injunctive norms. From an SCT perspective, learning that many others use MCs strengthened efficacy more effectively than observing a brief demonstration. Together, these insights highlight the potential and limits of Instagram Reels as tools for promoting menstrual health.