Circadian typology has been related to several mental health aspects such as resilience, perceived well-being, emotional intelligence and psychological symptoms and disorders. However, the relationship between circadian typology and emotion regulation, metacognitions and assertiveness, which constitute core constructs related to psychological well-being and psychopathology, remain unexplored. This study aims to analyze whether circadian typology is related with those three constructs, considering the possible influence of sex. 2283 participants (833 women), aged 18-60 years (30.37 ± 9.26 years), completed the reduced Morningness-Eveningness Questionnaire, the Emotion Regulation Questionnaire, the Meta-Cognitions Questionnaire 30, and the Rathus Assertiveness Schedule. Main effects were observed between circadian typology and cognitive reappraisal, metacognitions, negative beliefs of uncontrollability and danger, cognitive confidence, cognitive self-consciousness, and assertiveness (F(2,2276) > 4.80, p < 0.009, ηp2 > 0.004, in all cases). Morning-type participants scored lower than evening-type in general metacognitive beliefs, negative beliefs of uncontrollability and danger, cognitive confidence, and cognitive self-consciousness, and higher than evening-type in cognitive reappraisal and assertiveness, while neither-type exhibited intermediate scores (p < 0.033 in all cases). According to the results, evening-type individuals might display a higher tendency to support maladaptive beliefs about thinking itself as well as a lesser tendency to reappraise a potentially emotion eliciting situations in order to modify its meaning and its emotional impact and to exert their rights respectfully. This new evidence improves the understanding of the relationships between circadian typology and psychological factors related to psychological well-being and psychopathology. Results implications for the onset and maintenance of psychological problems are discussed. Although future longitudinal studies are needed, results emphasize evening-type as a risk factor for the development of psychological disturbances and morning-type as a protective factor against those.