Background: Effective health communication to encourage participation in COVID-19 preventive behaviours is crucial in helping mitigate viral spread. Intentions and beliefs are known determinants of adherence to these behaviours, therefore, health communication interventions based on these constructs may be effective. Visual languageless messages can be particularly useful in multilingual countries, where text-based communications can limit message exposure. This pre- and post-intervention study sought to identify the effect of exposure to languageless animated messages, presented in the Graphic Interchange Format (GIF), communicating COVID-19 preventive behaviours (physical distancing, handwashing, and mask-wearing) on behavioural intentions and beliefs. Methods: Between February and March 2021, a nationally representative sample of 308 Guatemalan adults completed this online survey experiment. Self-reported performance of preventive behaviours, understanding of COVID-19 transmission risk, as well as intentions, self-efficacy, and outcome expectancy beliefs about preventive behaviours were assessed at baseline. Participants were then exposed to a random combination of three of four possible GIFs in random presentation order. Following exposure to each GIF, intentions, self-efficacy, and outcome expectancy beliefs were reassessed. Results: In terms of main effects, GIF exposure was significantly associated with improved intentions, self-efficacy, and outcome expectancy beliefs in relation to physical distancing; intentions and outcome expectancy beliefs in relation to handwashing; and intentions and self-efficacy in relation to mask-wearing. These associations were not dependent on the combination of the three of four possible GIFs presented. Pairwise comparisons revealed that observed improvements in scores were most pronounced from baseline to the first GIF exposure and reduced thereafter. Conclusions: Exposure to languageless GIFs communicating COVID-19 preventive behaviours is associated with improvements in key social-cognitive determinants of those behaviours. Dosage of GIF exposure and durability of effects are issues that warrant further attention so we can better understand the conditions and point at which benefits are maximised. Moreover, the effect on behavioural adherence is yet to be determined. GIFs provide a valuable means to widely disseminate health messages via social media during public health crises, such as COVID-19. When these messages are languageless, the potential reach of dissemination can be maximised.