Purpose: To examine (a) the amount of health-related behavior, (b) the level of generalized optimism, (c) the belief about patients’ abilities to cope with difficult situations and obstacles and (d) the subjective sense of social exclusion at baseline and at follow-up among patients with chronic mental health issues participating in a psychosocial rehabilitation program in a community mental health setting. Materials and Methods: This prospective study involved 52 participants aged 18–43 years and diagnosed with mental illness who participated in a 6-month psychosocial rehabilitation program, organized within a special community setting. Different questionnaires were used: the Health-Related Behavior Questionnaire, the Revised Life Orientation Test, the General Self-Efficacy Scale, the Personal Competence Scale and a self-made questionnaire concerning social exclusion problems. Results: Statistical analysis of the questionnaire results taken at the beginning and end of the six-month course, running from November 2015 to May 2016, revealed significant increases in health-related behavior (p = 0.006) and general self-efficacy (p = 0.01). Conclusions: Psychosocial rehabilitation programs offered by community mental health settings might serve as an easy, accessible strategy to deal with different interpersonal and intrapersonal problems and as a potential way to improve health behavior. Further research is required to evaluate other psychosocial rehabilitation programs in different community mental health settings in Lodz Voivodeship, Poland.