The State-Trait Cheerfulness Inventory--Trait Version (STCI-T60) measures the temperamental basis of sense of humor involving theoretically derived personality dispositions of cheerfulness, seriousness, and bad mood. The reliability and validity of the newly developed STCI-T60 Italian version were assessed in a sample of Italian speakers (N = 683). Proper fit for a three-dimensional factor structure observed in previous studies was replicated and each factor demonstrated acceptable internal consistency and test-retest reliability. The associations between the STCI subscales and major personality dimensions, optimism, resilience, stress, and general well-being were further examined and results were in the expected directions (e.g., cheerfulness and bad mood being positively and negatively associated with well-being variables, respectively). Cross-cultural invariance examination was conducted to provide more validity data for the Italian STCI. Metric invariance was found between Italian and Canadian English speakers (N = 632), but scalar invariance was not shown.