--- - |2 Abstract The main aim of this study was to test whether mothers’ (n = 116) and fathers’ (n = 116) mind‐mindedness predicts infants’ physiological emotion regulation (heart rate variability; HRV) across the first year of life. Three hypotheses were examined: (a) parents’ mind‐mindedness at 4 and 12 months predicts infants’ HRV at 12 months over and above infants’ initial HRV levels at 4 months, (b) mothers’ and fathers’ mind‐mindedness independently predict infant HRV, and (c) the effects of mind‐mindedness on infant HRV (partially) operate via parenting behaviour. Infants’ HRV was assessed during rest and a stranger approach. Mind‐mindedness was assessed by calculating the proportions of appropriate and non‐attuned mind‐related comments during free‐play interactions, and parenting quality was observed at 4 and 12 months in the same interactions. Path analyses showed that mothers’ appropriate mind‐related comments at 4 and 12 months predicted higher baseline HRV at 12 months, whereas mothers’ non‐attuned comments predicted lower baseline HRV at 12 months. Similar, but concurrent, relations were found for fathers’ appropriate and non‐attuned mind‐related comments and infant baseline HRV at 12 months. In addition, fathers’ appropriate mind‐related comments showed an indirect association with infant baseline HRV at 12 months via fathers’ parenting quality. With regard to infant HRV reactivity during the stranger approach, mothers’ appropriate mind‐related comments at 4 months and fathers’ non‐attuned mind‐related comments at 12 months predicted a larger HRV decline during the stranger approach at 12 months. Infants’ HRV at 4 months did not predict parents’ later mind‐mindedness. The results indicate that mothers’ and fathers’ appropriate and non‐attuned mind‐related speech uniquely impacts the development of infants’ physiological emotion regulation. - Developmental Science, Volume 21, Issue 6, November 2018.