In two experiments we tested people’s naïve beliefs about where interventions act in real-world causal systems. We provided people with a description of a novel health condition that could be treated by two different treatments, a medication and a lifestyle modification. Participants judged a medication as acting on the symptoms of a disorder instead of the cause of the disorder, while a lifestyle modification was seen as acting on both the cause and the symptoms of a health condition (Experiment 1). These results held despite participants rating both treatments as effective. Providing information about the specific causal mechanism by which a treatment could work did not increase beliefs about a medication’s ability to target the cause of a disorder (Experiment 2). Implications for understanding of everyday causal interventions and health treatments is discussed.