Objective: To compare and evaluate the dietary quality of young and older sedentary Mexican-American women. Understanding key dietary concerns, while considering developmental transition periods and cultural relevance, can provide insight for developing appropriate nutrition interventions. Design: Cross-sectional dietary data were collected using unannounced 24 h diet recalls to assess nutrient intake adequacy (Estimated Average Requirement cut-point method) and dietary quality (Healthy Eating Index (HEI) 2010). Setting: Mujeres en Acción and Madres para la Salud, two community-based physical activity interventions. Subjects: Participants were 139 young (28 (SD 6) years) and 124 older (55 (SD 7) years) overweight/obese sedentary Mexican-American women (BMI = 25·0-35·0 kg/m 2 ) of low socio-economic status. Results: Older women consumed less Ca, Fe, folate, empty calories and energy from carbohydrate, but more fruit, vegetables, greens and beans, and fibre than younger women (all P < 0·05). Over 60 % of all participants had an intake below recommendations for fibre, Ca, vitamin E, vitamin C and folate. Both groups had low total HEI-2010 scores (62 for older and 63 for younger women; NS), with 57 % of older and 48 % of younger women classified as having a poor diet. Conclusions: Despite differences in nutrient requirements according to developmental transition periods (childbearing v. perimenopausal), overall, older and younger Mexican-American women generally had low-quality diets and may benefit from dietary quality improvement.