Purpose: To assess the efficacy of primary sternal closure technique compared to vacuum-assisted closure technique in treatment of post-cardiac surgery mediastinitis in paediatric age group. Additionally, assessed postoperative need for IV drug use, hospital stay length, wound and sternal healing and survival. Hypotheses: primary sternal closure is a reliable technique for treatment of poststernotomy mediastinitis following cardiac surgery in paediatric age group. Materials and methods: A prospective randomized controlled trial included 217 pediatric patients developed post-cardiac surgery mediastinitis from 2016 to 2022. They were randomly divided into primary sternal closure group (A) and vacuum-assisted closure group (B) and operated by two cardiothoracic surgeons. Follow-up of the patients was done for 6-months duration following treatment of mediastinitis to assess postoperative need for hospitalization, IV drug use, wound complications, sternal stability and survival. Results: The final analysis included 101 patients in each group. The chance of survival over 6 months after surgery was more for primary sternal closure group (175.2) days versus (157.6) days for the vacuum-assisted closure group, with significant difference Log Rank test p-value (0.005). Duration for IV antibiotics use in the primary closure group was 8.55±3.57 and it was 32.61±8.39 showing high statistically significant difference (p<0.001). Patients in the primary closure group had earlier discharge from hospital 15.77±4.18 than vacuum assisted group 42.61±8.39, with high statistically significant difference (p<0.001). Primary closure group showed better sternal stability and sternotomy wound healing on clinical follow-up