The work of a mental health social worker will depend on their work environment (private practice vs. working for a non-profit, for example) and how they provide treatment (individual vs. group, for example). They may gain clients based on referrals in the setting they work in or clients may seek them out through therapist services and recommendations. They perform work that is similar to counselors and they make up one of the largest groups of mental health service providers. They work with at-risk and vulnerable populations as well.