This cross-sectional study examined how food-related behaviours and nutrient intake are associated with nutritional status among 393 adults enrolled in Community-Based Treatment and Rehabilitation (CBTaR) programmes in Kelantan, Malaysia. Using structural equation modelling, the study found that nutrient intake was the strongest predictor of nutritional status, while food-related behaviours significantly influenced nutrient intake. Drug use profiles were also associated with both eating behaviours and nutritional status. Younger age, unemployment, and lower education were linked to poorer nutritional outcomes. The findings highlight the importance of integrating nutrition counselling, food literacy education, and behavioural support into substance use disorder rehabilitation programmes to improve recovery outcomes and long-term health.