Approximately 34% of global greenhouse gas emissions are attributable to food systems(1). At the individual level, shifting dietary patterns to include more plant-based foods and consuming fewer animal-based foods can reduce environmental impacts while supporting human health(2). However, information and education alone may be insufficient to achieve sustained dietary change. Behaviour change techniques may therefore be important components of interventions promoting sustainable food consumption. This systematic review aimed to identify and describe the behaviour change techniques used in individual-level, sustainability-framed dietary interventions and to examine associated dietary and diet-related environmental outcomes. The involvement of health professionals in intervention delivery was also examined. Randomised controlled trials, quasi-experimental studies and pre-post intervention studies with or without a control group were eligible. Studies were required to include adults, evaluate an individual-level intervention explicitly framed around environmental sustainability, and measure changes in dietary intake or diet-related environmental outcomes, such as greenhouse gas emissions, land use or water use. PubMed, Web of Science (Core Collection), MEDLINE (via EBSCO), CINAHL (via EBSCO) and Cochrane CENTRAL were searched from database inception to 1 May 2026. The review was prospectively registered with PROSPERO (CRD420261341730). Behaviour change techniques were classified using the Behaviour Change Technique Ontology(3), and methodological quality was assessed using the Academy of Nutrition and Dietetics Quality Criteria Checklist for Primary Research. Due to heterogeneity in intervention designs and outcome measures, findings were synthesised narratively. Following screening of 4,315 records, 38 studies met the inclusion criteria. Interventions varied in their duration, mode of delivery and targeted dietary behaviours. Included studies incorporated between 2 and 26 behaviour change techniques per intervention. Overall, 44 unique behaviour change techniques were identified, with 243 instances of use across the included interventions. The most frequently identified techniques were “deliver informational support”, “instruct how to perform behaviour”, “inform about negative environmental consequences”, “inform about positive health consequences” and “self-monitor behaviour”. Only six studies involved a health professional in intervention delivery. Across the included studies, reported improvements included reduced meat and animal-source food consumption, increased plant-based food consumption and lower diet-related environmental impacts, particularly greenhouse gas emissions. A range of behaviour change techniques were used in interventions reporting positive outcomes, although findings varied across studies and outcome categories. This review provides a systematic classification of the behaviour change techniques used to promote sustainable dietary behaviours among individuals. The findings may inform the design of evidence-informed sustainable diet interventions that can be translated into dietetic practice to help reduce diet-related environmental impacts and mitigate climate change.