AbstractOnly a few studies have investigated the association between psychological stress and the healthfulness of plant-based diets while accounting for variances in age groups and regions. In light of this, this study aimed to identify the food groups that contribute the most to the relationship between the healthfulness of plant-based diets and psychological stress in female students in Saudi Arabia. This cross-sectional study, which included 401 female college students aged 19–35 years, collected data on blood, anthropometric indices, the perceived stress scale-10 (PSS-10) and diet using the Saudi food frequency questionnaire. An overall plant-based diet index (PDI), healthy PDI, and an unhealthy PDI (uPDI) were defined. Multiple linear regression analyses were applied to examine the associations between PSS-10 and PDI and hPDI and uPDI. No associations between the PSS-10 score and the overall PDI or uPDI scores were found; however, a six-point higher hPDI score was associated with a 0·16-point lower PSS-10 score (95 % CI, –0·24, –0·08) after controlling for lifestyle factors. Moreover, adjustments for healthy food groups, including vegetables and fruits, attenuated the association between the hPDI and PSS-10. In conclusion, healthy plant-based diets are associated with lower psychological stress in young Saudi women. This finding highlights the importance, especially for female students, of following diets that are not only plant-based but are also healthy and rich in fruits and vegetables.