Background: Positive thinking is a cognitive attitude that focuses on optimism and aims for positive results. Positive thinking leads to positive emotions, more adaptive behaviors, and better problem solving. Positive thoughts can inspire individuals and have been linked to increased psychological health. On the other hand, negative thoughts are related to unsatisfactory mental health. Objectives: This study aimed to analyze the factor structure and psychometric properties of the Portuguese version of the Positive Thinking Skills Scale (PTSS) and to verify the correlations between positive thinking, resilience, and repetitive negative thinking. Participants: The sample comprised 220 Portuguese participants between 18 and 62 years of age (M= 24.9,SD= 6.58), and the majority were women (80.5%). Method: Participants responded to an online sociodemographic questionnaire, the PTSS, the Persistent and Intrusive Negative Thoughts Scale (PINTS), and the Resilience Scale-10 (RS-10). Results: Confirmatory factor analysis results indicated that the original one-factor structure of the PTSS obtained good fits. An excellent value of internal consistency was found. The results also revealed convergent and discriminant validity. Conclusion: The PTSS is a brief and reliable instrument for assessing positive thinking skills, and its use in research is recommended.