People with mental illness may need the support of caregivers in certain areas of their lives, and there is an increasing need for quality care for people with mental health problems by qualified health professionals. Often, these professionals may develop so-called burnout syndrome, although some authors point out that positive emotions may also arise. In addition, several variables can act as both protectors and stressors. Therefore, the main aim of the current study is to identify variables related to the professional care of people with mental illness (i.e., protective or stressor variables) through a systematic review. The review was conducted according to the PRISMA guidelines with a final selection of 20 articles found in the Web of Science, PubMed, ScienceDirect and Dialnet databases between the months of October and November 2019, and updated in June 2022. The results show that job satisfaction is a strong predictor of the quality of care, and that congruence between personal and organizational values is a very important factor. Meanwhile, working in the same job for successive years, working in community mental health teams and experiencing burnout act as stressors and reduce the quality of care provided.