Moral appeals are rhetorical devices appealing to deep-seated and trans-situational moral foundations. Empirical research on the effects of moral appeals, especially those in visual format, on persuasiveness and retransmission remains scarce. In the domain of tobacco control, this dissertation presents data from four experiments to address this gap. Study 1 presented a case study where a specific type of moral appeal—visual portrayals of secondhand vaping within electronic cigarette video advertisements—was found to increase anti-vaping beliefs, emotions, and policy opinions despite the presence of pro-vaping verbal arguments. Encouraged by these preliminary findings, in Study 2 I expanded the stimuli pool to include 122 textual anti-vaping messages (TAVMs) and 90 pictorial anti-smoking messages (PSAMs), all scaled along the care, purity and liberty moral dimensions through a crowdsourcing and aggregation procedure. Then, I employed a multiple-message randomized design and found that care and purity appeals increased perceived effectiveness (PE). Evidence also supported the moral matching hypothesis predicting PE in the case of care-based PASMs but not for other types of moral appeals. Study 3 and Study 4 address the outcome of retransmission. After gathering preliminary evidence supporting the retransmission-boosting effects of care-based PSAMs in Study 3, I carried out a confirmatory test in Study 4 with the additional manipulation on user-generated comments to operationalize social influences. Results not only confirmed the main effects of care-based PSAMs to increase retransmission intentions, but also corroborated the operation of morality through auxiliary moderation and mediation analyses. Moreover, even when campaign-disparaging comments inhibited retransmission, the retransmission-boosting effects of care-based PASMs nevertheless persisted. In a health context, this dissertation provided the first set of experimental evidence supporting that moral appeals, especially those in visual format, can persuade and spread, but not uniformly. Care-based visual moral appeals are particularly promising to help optimize both reach and influence for digital communication campaigns. Insights from moral psychology should be considered to advance our understanding of the roles of moral appeals and social influences in digital persuasive messaging.