OBJECTIVES: Mental stress, low health literacy (HL) and nutrition literacy (NL) are associated with serious negative health outcomes. The aim of this study was to investigate HL and NL levels, in relation to levels of perceived stress, in adults. METHODS: This cross-sectional study was conducted in the urban area of the Attica region, Greece. The sample consisted of 1,281 individuals, aged ≥ 18 years. The European Health Literacy Questionnaire 47, the Greek version of the Nutrition Literacy Scale and the Perceived Stress Scale 14 were used. Socio-demographic characteristics were also assessed. Nonparametric Mann-Whitney U and Kruskal-Wallis tests, Pearson chi-square and multiple linear regression models were used. RESULTS: The sample's perceived stress mean value (SD) was 26.47 (7.27) with women scoring statistically significantly higher than men. The mean HL and NL scores were 32.28 (8.28) and 22.11 (5.67), respectively. Linear regression analysis has shown that perceived stress was significantly negatively associated with HL (p < 0.001) but not with NL levels (p = 0.675) after adjusting for a series of confounding variables. CONCLUSIONS: Low health literacy seems to be very significantly associated with high levels of perceived stress. The reasons behind this association require further investigation.