Objective: The aim of this study was to explore the acute psychosocial risk in families with infants undergoing surgery for a congenital heart disease and, secondarily, to explore the psychosocial impact of antenatal versus post-natal diagnoses. Method: The study sample comprised 39 caregivers (28 mothers) of 29 children diagnosed with a congenital heart disease and requiring surgery within the first 4 weeks of life. Psychosocial risk was measured using the Psychosocial Assessment Tool, which was adapted to include four novel items examining infant risk factors, namely, sleeping, feeding, crying, and bonding difficulties. Parents’ psychosocial risk was measured within 4 weeks after their child's surgery and stratified into a three-tiered framework: Universal, Targeted, and Clinical risk. Results: Of the total sample, 61.5% of parents were classified as Universal, that is, at lowest risk; 35.9% as Targeted, and 2.6% as Clinical. The within-family parent total Psychosocial Assessment Tool score correlations were non-significant, and there were no differences between families of infants who received post-natal versus antenatal diagnosis or single ventricle versus biventricular repair. Linear regression found that a higher parent education significantly predicted a lower total Psychosocial Assessment Tool score. Conclusions: Findings indicate that, although the majority of parents adapt to the acute stress of surgery for a serious cardiac illness in their infant, the remaining 38.5% report an increased psychosocial risk associated with higher rates of emotional distress, which may impact on the parental quality of life and capacity for optimal parenting. The distribution of psychosocial risk in parents of children undergoing surgery for a congenital heart disease is consistent with that described for parents of children with other serious paediatric diagnoses.