Interoceptive sensitivity is an essential component of recent models of “the self.” Increased focus on the self (e.g., self-observation in a mirror) can enhance aspects of self-processing. We examined whether self-observation also enhances interoceptive sensitivity. Participants performed a heartbeat detection task while looking at their own face in a mirror or at a black screen. There was significant improvement in interoceptive sensitivity in the mirror condition for those participants with lower interoceptive sensitivity at baseline. This effect was independent of the order of conditions, gender, age, body mass index, habitual exercise, and changes in heart rate. Our results suggest that self-observation may represent a viable way of manipulating individuals' interoceptive sensitivity, in order to directly test causal relations between interoceptive sensitivity and exteroceptive self-processing.