Health anxiety involves persistent worry about one’s health and beliefs one has an illness or may contract a disease. The interpersonal model of health anxiety (Noyes et al., 2003) is a conceptual framework linking insecure attachment to health anxiety. The present study, clarified the contribution of insecure attachment to health anxiety by studying two key dimensions of insecure attachment: anxious and avoidant attachment. The unique role of insecure attachment in health anxiety was tested by controlling for emotional instability. The potential interaction between attachment insecurity and emotional instability in predicting health anxiety was also tested using hierarchical regression analyses with data from 147 undergraduates. Anxious attachment uniquely predicted health anxiety even when avoidant attachment and emotional instability were taken into account. An interaction was also observed where high anxious attachment and high emotional instability combined to predict higher health anxiety. This interaction was specific to health anxiety (versus depressive symptoms). An unexpected interaction was found where high avoidant attachment and low emotional instability combined to predict lower health anxiety. The present study extends research on health anxiety by clarifying the nature of insecure attachment in and the role of emotional instability in the interpersonal model of health anxiety.