Individuals diagnosed with psychosis may experience difficulties in managing their chronic diseases due to cognitive and emotional challenges. Evaluating the self-care agency, self-management, and adaptation to illness of these patients is crucial for understanding their capacity to maintain their health. This study aimed to assess the level of chronic disease management among patients diagnosed with psychotic disorders. This cross-sectional descriptive study was conducted with 70 female patients in the women's ward of a regional psychiatric hospital. All participants were followed up for at least one year and had at least one chronic disease in addition to a psychosis diagnosis. Data were collected using a patient information form, the Positive and Negative Syndrome Scale (PANSS), the Self-Care Agency Scale (SCAS), and the Chronic Disease Self-Management Scale (CDSMS). Among the participants, 64.3% were ≥ 40 years old, 54.3% were married, and 82.8% had a secondary or higher level of education. Additionally, 58.6% were smokers, 65.7% were diagnosed with non-organic psychosis, and 25.7% had chronic diseases for more than six years. Comorbidities included diabetes mellitus (31.4%), thyroid disorders (45.7%), and hypertension (17.2%). A negative correlation was found between total scores on the PANSS and SCAS (r = -0.61, p < 0.01). Furthermore, strong positive correlations were observed between the total score of the SCAS and subdimensions of the CDSMS, including self-stigma, coping with stigma, treatment adherence, and healthcare efficacy (p < 0.01). These findings indicate that severe psychotic symptoms negatively impact patients’ self-care abilities, and stigma reduces treatment adherence.