This PhD thesis maps out how the minimal language approach (Goddard, 2018a, 2021b; Sadow, 2020; Wierzbicka, 2018b) can be applied to Australian public health posters to improve their accessibility and cross-translatability. The minimal language approach has roots in decades of cross-linguistic research and is a practical adaptation of the Natural Semantic Metalanguage (NSM). It is designed to address communicative challenges in a diverse range of fields. Research (e.g., Szmuda et al., 2020) consistently finds that the wording of public health messages is inaccessible to the general population. While approaches such as Plain Language (e.g., Eagleson, 1998) are often implemented to combat accessibility problems, studies indicate that the effectiveness of such approaches can vary (Kauchak & Leroy, 2016). Scholars have therefore called for a more systematic, research-based and linguistic approach to public health messaging (Burns & Kim, 2011). The translatability of English language health messages has also been highlighted as something that deserves more dedicated linguistic research (e.g., Dew et al., 2018). Translations of health messages are often found to be inaccessible, lacking and flawed (Dawood, 2022; Pym et al., 2022). Scholars have identified a need to decentre English monolingual ideologies (Zhang & Wu, 2020), and to author English health messages so they are optimised for translation to foster better and more efficient outcomes (Goddard, 2019). Further, while scholars agree that some visuals help aid understanding of health messages (e.g., Manno et al., 2018; Park, Zuniga, & Lee, 2016), research into this topic is scarce. To capture the full, polysemiotic scope of public health posters, this thesis proposes a novel, transdisciplinary framework that combines the minimal language approach with insights from cognitive semiotics and translation theory. Guided by this theoretical framework, a five-part empirical investigation was undertaken. [...]