Positive cognitions contribute directly to psychological well-being, whilst negative cognitions are associated with many mental disorders including depression and anxiety. Psychometric properties of the Oxford Positive Self-Scale were analyzed in a Turkish sample group to assess positive beliefs about the self. In this context, two studies were conducted with two different sample groups. Study I included 403 participants (57 % female, mean age: 25.66) and Study II included 375 participants (56 % female, mean age: 26). Confirmatory factor analyses conducted within the scope of Study I confirmed the 8-item short form of the scale with a 4-factor structure. Configural, metric and scalar analyses also confirmed the measurement invariance. Reliability analyses showed that the scale was in the acceptable reliability range. Item Response Theory analysis provided discrimination. Furthermore, positive self was positively correlated with openness, conscientiousness, extraversion, agreeableness, subjective happiness, self-esteem and negatively correlated with neuroticism. Structural equation modeling in Study II revealed that psychological distress and subjective wellbeing mediate the relationship between positive self-regard and psychological well-being, highlighting their roles in predictive validity analysis. The results suggest that the Oxford Positive Self-Scale short form is valid and reliable for assessing individuals' positive self-cognitions. •The Oxford Positive Self Scale (OxPos) measures people's cognitions of happiness.•OxPos-short form is in the acceptable validity and reliability range in Turkish.•The present study was carried out with two separate sample groups.•Positive self is negatively associated to anxiety, stress, and depression.•Positive self and psychological well-being are mediated by distress and vitality.