Abstract Background Right ventricular volume overload (RVVO) is one of the most important hemodynamic characteristics in children with congenital heart disease (CHD) and heart failure, and cardiomyocyte (CM) proliferation is one of the most vital factors for improving cardiac performance. However, whether and how RVVO reboots CM proliferation remains elusive. Methods and results We first created a neonatal RVVO mouse model via abdominal aorta and inferior vena cava-fistula microsurgery at postnatal day 7 (P7), the edge of CM proliferation window. We subsequently performed bulk RNA-seq, single cell RNA-seq/flow cytometry, and immunofluorescence staining on the right ventricles (RV) of RVVO mice at P14/P21, defined as prepubertal stage, revealing that RVVO temporarily reboots prepubertal CM proliferation via immune responses. Conclusions In considering the importance of RVVO and CM proliferation, this study may bring an opportunity to create a novel paradigm to treat pediatric CHDs or heart failure. Graphical Abstract