Legally mandated treatment is common in the criminal justice system, for example, for anger management, substance misuse, and intimate partner violence. Past studies have compared voluntary and legally mandated treatment participants but have not distinguished a third, in-between group that is formally pressured to participate in treatment, but not mandated by the criminal justice system. The current study aimed to assess differences on individual characteristics (e.g., sociodemographic and psychiatric) and baseline measures of psychopathology (e.g., anger, aggression, and depression) across three levels of voluntariness and to determine whether voluntariness was associated with treatment recommendation, refusal, and completion at an outpatient anger treatment clinic. Data were retrospectively gathered from the clinical charts of 405 participants. Referrals were classified as voluntary (e.g., self-referred, 61%), formally pressured (e.g., required by work, 14%), or legally mandated (e.g., court order, 25%). Legally mandated participants were younger, more likely to have substance use disorder, less likely to be women, to have a high school education, or to be on psychiatric medications compared to the other two groups. Voluntary participants scored higher on measures of self-reported anger, depression, and stress than the legally mandated participants. Legally mandated participants in particular presented with non-clinical levels of anger and aggression. Level of voluntariness did not affect the decision to recommend individual or group therapy after an intake assessment, but legally mandated participants were significantly more likely ( OR = 2.30) than voluntary participants to refuse recommended treatment. Level of voluntariness did not have a significant association with treatment completion. Findings support our distinction between legally mandated and formally pressured participants, but do not support previous research that suggests legally mandated individuals have lower attrition rates in similar treatment programs. The study has implications for the criminal justice system and for anger treatment programs who admit participants with varying levels of voluntariness.