Introduction: A Mediterranean diet (MD) meets several important criteria for a healthy diet. This dietary pattern may be beneficial for psychological function. The aim of this study was to investigate the relationship between the adherence to MD and psychological performance in young women. Material and methods: The study included 181 volunteers with an average age of 20.8 ± 1.7 years. Neuropsychological performance was assessed using a number of standard instruments, including Cognitive Ability Questionnaire (CAQ), Depression Anxiety Stress Scales (DASS-21), Insomnia Severity Index (ISI), Epworth Sleep Scale (ESS) and Quality of Life Questionnaire (QLQ). A validated food frequency (FFQ) questionnaire, that included 65 types of foods, was used to evaluate the amount of different food types consumed. Results: The individuals in the lowest quartile for the MD pattern had a significantly higher prevalence of a high stress score, poorer quality of life, and higher degrees of insomnia and sleepiness during the day than the highest quartile. Linear regression showed an inverse relationship between fruit consumption and stress scores (b = 0.012; p = 0.022) and a direct relationship with quality of life (b = 0.005; p = 0.043). The monounsaturated fatty acid (MUFA)/Saturated fatty acids (SFA) ratio was negatively related to the insomnia score (b = 53.0; p = 0.043). Dairy products were significantly associated with stress scores (b = 0.011; p = 0.035). Dietary meat products were also directly related to stress and insomnia scores (b = 0.021; p = 0.049 and b = 0.015; p = 0.049, respectively) and reversely associated with a score of cognitive abilities (b = –0.034; p = 0.032). Conclusions: Adherence to a MD is associated with a lower degree of stress, insomnia and daytime sleepiness, as well as higher quality of life.