Introduction: Specialized psychosocial care centers (Centros de Atenção Psicossocial [CAPS]) are mental health services focused on social rehabilitation and reducing hospitalization of patients with severe and persistent mental illness. Collective multiprofessional activities (CMPA) are the main therapeutic tools used at CAPS. This study aimed to determine rates of adherence to CMPA and identify factors associated with adherence. Methods: This is a cross-sectional study in which 111 CAPS users were evaluated using questionnaires covering patient characteristics, clinical status, and treatment and incorporating the Functioning Assessment Short Test (FAST), the Clinical Global Impression – Severity scale (CGI-S), and the Clinical Global Impression – Improvement scale (CGI-I). Adherence was defined as attendance at 50% or more CMPA during the previous 3 months. Data were analyzed using descriptive statistics, bivariate analysis, and Poisson logistic regression with robust variance to estimate prevalence ratios. Results: CPMA adherence was 43%. Having children aged 14 years or younger was significantly associated with non-adherence (71%, p = 0.001). Poor or partial adherence to psychotropic drugs tended to be associated (p = 0.066) with poor adherence (33% higher risk), as was the number of psychiatric hospitalizations during CAPS (p = 0.076), with a cumulative association of 5% non-adherence per hospitalization. Conclusions: CMPA adherence was low in the study. It is necessary to consider the environment in which the individual lives and invest in support networks, providing patients and family members with explanations about the importance of CMPA to rehabilitation and attempting to tailor the care provided to each patient’s needs. There was an association between greater number of psychiatric hospitalizations and non-adherence, suggesting that CAPS are fulfilling a preventive role.