Background: The latency to reparation of interactive mismatches (interactive repair) is argued to regulate infant distress on a psychobiological level, and maternal anxiety disorders might impair infant regulation. Sampling and Methods: A total of 46 dyads (19 mothers with an anxiety disorder, 27 controls) were analyzed for associations between interactive repair and infant cortisol reactivity during the Face-to-Face-Still-Face paradigm 3-4 months postpartum. Missing cortisol values (n = 16) were imputed. Analyses were conducted on both the original and the pooled imputed data. Results: Interactive repair during the reunion episode was associated with infant cortisol reactivity (original data: p < 0.01; pooled data: p < 0.01) but not maternal anxiety disorder (p > 0.23). Additional stepwise regression analyses found that latency to repair during play (p < 0.01), an interaction between distress during the first trimester of pregnancy and latency to repair during reunion (p < 0.01) and infant self-comforting behaviors during the reunion episode (p = 0.04) made independent contributions to cortisol reactivity in the final regression model. Conclusions: This is the first study demonstrating that interactive repair is related to infant psychobiological stress reactivity. The lack of a relation to maternal anxiety disorder may be due to the small sample size. However, this result emphasizes that infants respond to what they experience and not to the maternal diagnostic category.