Disengagement from services by people with serious mental illnesses continues to be a major challenge for the mental health system. Assertive community treatment combined with Housing First services is an intervention targeted toward consumers whom the system has failed to engage. The processes involved in engaging and maintaining consumers in mental health services play an important role but remain an understudied aspect of the intervention. This study examined the social interaction between consumers and case managers from the perspective of consumers. Seventy service contacts between unique consumer–case manager dyads were sampled. Consumers with co-occurring serious mental illness and substance use disorders completed interviews after each service contact. They provided information on sociodemographic characteristics, service contact characteristics, consumer-provider relationship, utilization of coercive strategies, perceived coercion, and service contact evaluation. Multivariate regression analyses examined the association of consumer-provider relationship and perceived coercion with service contact evaluation. Consumer-provider relationship was negatively associated with perceived coercion (effect size=. 08). Perceived coercion was negatively associated with service contact evaluation (effect size=. 34). Perceived coercion was positively associated with time in the program (effect size=. 17) and negatively associated with length of the service contact (effect size=. 14). Effect sizes ranging from. 08 to. 34 are typically considered small to medium. Findings demonstrate that for consumers, a positive response to service contacts indicated that they did not feel coerced. With consumers whose connection to services is tenuous, an immediate positive response to service contacts may be vital to maintain engagement. Research is needed to identify supportive case manager strategies that facilitate relationship building.(Psychiatric Services 60: 183–188, 2009)