Semi-structured qualitative interviews were conducted with 26 African American men with serious mental illness who were consumers of community mental health services and 26 members of their social support networks. All participants were asked what they believed had caused the consumers’ mental illness. Consumer participants most commonly identified chronic life stressors as a causal factor, while social supports most often identified intrinsic factors such as genetics or biology as causes of mental illness. Some support participants believed that unintentional drug use had precipitated the onset of mental illness or had no causal theories. The fact that some support participants could not identify a causal explanation may indicate failure on the part of mental health care systems to engage with consumers’ social support networks and provide education about mental illness and its causes. The implications of etiology beliefs on mental health service utilization are discussed.