Previous research had associated early maladaptive schemas, cognitive fusion and psychological needs. However, a deeper understanding of these relationships is needed regarding mediational effects of schemas on psychological needs and symptomatology. We aimed to explore the relationships between schema domains, cognitive fusion, psychological needs and symptoms. Therefore a clinical sample composed of 58 individuals with psychiatric diagnosis, who filled self-reported questionnaires was reanalyzed on a cross-sectional design. Medium to strong correlations between schema domains and dialectical polarities of psychological needs were found. Cognitive fusion mediated the relationship between schema domains with symptomatology. Also, the relationship between psychological needs and disconnection and rejection and overvigilance and inhibition domains was mediated by cognitive fusion. Schema domains are strongly related with the regulation of psychological needs and symptomatology. These results may be important not only to transtheoretical and integrative case conceptualization but also to clinical decision-making tailored to the patient’s characteristics, styles of communication and needs.