Abstract Background Important differences in the mechanism of respiration between adults and children warrant distinction in the management of diaphragmatic paralysis as a complication of cardiac surgery. We describe the management and outcomes of this complication in both groups. Methods We retrospectively analyzed 16 patients (5 adults and 11 children) with diaphragmatic paralysis after cardiac surgery performed between 2008 and 2018. Clinical examination, chest radiography, and confirmation with fluoroscopy in selected cases were our modalities of diagnosis. All adults were managed conservatively, whereas plication was performed in all children. Results The incidence of diaphragmatic paralysis was 0.98% in pediatric patients and 0.43% in adults. The mean age was 2.33 ± 2.59 years in children and 53.2 ± 17.99 years in adults. All adults were symptomatic. All children showed difficulty in weaning from mechanical ventilation after cardiac surgery. The period of mechanical ventilation before plication was 2–6 days (median 4 days). Death occurred as a result of low cardiac output in a 10-year-old boy, and due to respiratory failure in a 30-year-old woman. Children were successfully weaned from mechanical ventilation after diaphragmatic plication. The median time to extubation after plication was 2.5 days (range 1–13 days). The median period of recovery in adults was 52 days (range 32–85 days). All survivors had acceptable outcomes at 6 months to one year. Conclusion Conservative management in adults and early plication in children are viable treatment options for diaphragmatic palsy after cardiac surgery, with acceptable outcomes. Keywords Cardiac surgical procedures, coronary artery bypass, diaphragm, heart defects, congenital, peripheral nerve injuries, respiratory paralysis