Current food production and consumption patterns are contributing to climate change, biodiversity loss and environmental pollution, undermining the health of current and future generations (1). The EAT-Lancet Commission called for a Great Transformation of our food system including a population-wide shift to more environmentally sustainable diets (2). Nutrition professionals are well-positioned to contribute to this transformation. However, interventions that support workforce capacity in this area remain limited. In 2023, Dietitians Australia’s food and environment interest group members developed the PlanEATary Quest, a choose-your-own-adventure that prompts self-reflection and inspires environmentally sustainable dietary behaviour change. The intervention was designed to promote twelve specific healthy, sustainable diet-related practices (3). This study presents the results from a pilot of the PlanEATary Quest with nutrition and dietetics professionals employed at a large health service in Victoria’s eastern suburbs. This mixed-methods case study examined whether participation influenced self-reported sustainable dietary behaviours and knowledge, and identified factors that helped or hindered engagement with the intervention. Participation in the PlanEATary Quest involves completion of a 12-question self-assessment dietary questionnaire at baseline, a self-designed 3-week experiential challenge, and a post-challenge questionnaire. Quantitative data from the pre-post surveys were analysed using a paired-sample t-test and a Wilcoxon signed-rank test. Participants were invited to complete a qualitative survey or interview upon completion of the PlanEATary Quest to reflect on factors that influenced their engagement with the intervention. This qualitative data were thematically analysed deductively, guided by the Consolidated Framework for Implementation Research. Analysis of pre-post questionnaires (n = 40) revealed statistically significant improvements (p < 0.05) in six of the twelve desired dietary behaviours; (i) sourcing sustainable food, (ii) knowledge regarding Australian native ingredients (which had the lowest pre-challenge score) (46/90), (iii) sourcing from local food systems, (iv) in-season produce purchase, (v) consumption of diverse plant foods and (vi) frequency of meat consumption. Interviews and surveys revealed three overarching themes of factors that influenced participants' engagement; (i) individual attitudes and values, (ii) workplace culture and leadership support, and (iii) delivery of the intervention. These factors may influence engagement with professional development activities in general or specifically sustainable food systems content, and should be considered when designing and delivering similar workforce interventions. Applying these lessons to future efforts to strengthen workforce capacity of nutrition and dietetic professionals may support greater engagement and efficacy. The PlanEATary Quest may provide a readily available intervention to promote the adoption of healthy, sustainable dietary behaviours at an individual level, and potentially support workforce capacity to promote these desired behaviours amongst the communities we work with. Such experiential, interactive interventions may be a valuable tool to mobilise and support the nutrition and dietetics profession as we contribute to food systems transformation.