Medically complex children including infants undergoing cardiac surgery are at increased risk for hospital readmissions. Investigation of this population may reveal opportunities to optimize systems and coordination of care. A retrospective study of all infants undergoing cardiac surgery from 2015 through 2016 at a large tertiary institution who were readmitted within 1 year of discharge from cardiac surgical hospitalization was performed. Data specific to patient characteristics, surgical hospitalization, and readmission hospitalization are described. Unplanned readmissions within 1 year of hospital discharge were analyzed with Cox proportional hazard regression to identify factors associated with increased hazard for earlier unplanned readmission. Comparable to previous reports, 12% (78/658) of all surgical hospitalizations were associated with unplanned readmission within 30 days. Infectious etiology, followed by cardiac and gastrointestinal problems, was the most common reasons for unplanned 30-day readmission. Unplanned readmissions within 2 weeks of discharge were multifactorial and less commonly related to cardiac or surgical care. Primary nasogastric tube feeding at the time of discharge was the only significant risk factor for earlier unplanned readmission (p = 0.032) on multivariable analysis. Increased care coordination with particular attention to feeding and comorbidity management may be future targets to effectively mitigate readmissions and improve quality of care in this population.