The aim of this study was to evaluate the impact of a social contact and education intervention to improve attitudes to mental illness in first-year social work students. This was a 3-month cluster randomized controlled trial with two parallel arms: intervention (87) and control group (79). The intervention was a workshop led by an OBERTAMENT activist (a person with a mental illness trained in communication skills and empowerment by a social worker). We assessed intended future behavior toward people with mental illness, personal and perceived stigma, and mental health–related attitudes (self-reported questionnaire). The intervention improved social work students’ attitudes (d 0.50, p < .05) and reduced personal stigma toward people with mental illness (d = 0.35, p = .04) as well as improving their future intended behavior 2 weeks after the intervention (d = 0.51, p = .01). The intervention impact on authoritarian attitudes toward people with schizophrenia was maintained after 3 months (d = 0.94, p = .01). Long-term impact needs to be improved.