Purpose <p>Healthy and sustainable diets promote individual health and well-being while minimizing environmental impact. Although the concept of sustainable diets has gained increasing attention, the extent to which nutritional adequacy aligns with overall dietary sustainability remains unclear, particularly in the Portuguese context, where dietary patterns reflect both Mediterranean and Western influences. The study aims to assess the association between sustainable and healthy diet adherence and nutritional adequacy among Portuguese adults.</p> Methods <p>Data was gathered using a self-administered questionnaire between October and December 2022 from 347 adults. The Sustainable and Healthy Eating Diet index was used to assess adherence to a sustainable and healthy diet. A semi-quantitative food frequency questionnaire was used to record dietary consumption. Nutrient inadequacy was defined as an intake below the dietary reference values set by the European Food Safety Authority for 18 selected nutrients.</p> Results <p>The prevalence of inadequacy for dietary fibre, vitamins A, E, C, folate and potassium was higher in participants with low adherence to a sustainable and healthy diet. After adjusting for confounders, participants with higher adherence to a sustainable and healthy diet were less likely to have inadequate intake of dietary fibre (OR = 0.14, 95% CI: 0.06,0.32), vitamin A (OR = 0.11, 95% CI: 0.02, 0.54), vitamin E (OR = 0.13, 95% CI: 0.06, 0.29), B6 (OR = 0.26, 95% CI: 0.09, 0.81), folate (OR = 0.14, 95% CI: 0.06, 0.31), vitamin C (OR = 0.19, 95% CI: 0.09, 0.43), selenium (OR = 0.35, 95% CI: 0.12, 0.99), and potassium (OR = 0.19, 95% CI: 0.07, 0.51). Participants with higher adherence to a sustainable and healthy diet were also less likely to have six or more inadequacies in nutrient intake (OR: 0.08, 95% CI: 0.03, 0.23).</p> Conclusion <p>Individuals who more closely follow a sustainable and healthy diet tend to achieve better nutritional adequacy.</p>