Community-based health interventions have emerged as a growing focus for anthropological research. The application of ethnographic approaches in clinical practice settings reveals that community-based interventions must grapple with "noise," or unanticipated factors such as patients' own perceptions of illness and treatment, primary care providers' non-adherence to guidelines-based treatment, the social dynamics of the clinic site itself, and incomplete understanding and acceptance of an intervention by a clinic's staff members. Such noise can influence the implementation and quality of treatment. Thus, identifying clinic-based noise is critical in assessments of fidelity to intervention protocols as well as outcomes of community-based interventions. This paper highlights findings from an evaluation of a mental health intervention focusing on the role of promotoras (briefly trained, non-professional community health workers) as mental health practitioners in two urban New Mexico, USA, community health centers. Our research identified three areas of clinic-based noise: the clinics' physical ability to "absorb" the intervention, the challenges of co-worker instability and interpersonal relationships, and balancing extra workplace demands. The findings demonstrate the value of ethnographic approaches in community-based intervention research.