Cardiac catheterization is an invasive diagnostic and treatment tool for congenital heart disease (CHD) with potential complications. To describe the immediate outcomes of patients who underwent cardiac catheterization for CHD at the Uganda Heart Institute (UHI). The study was a retrospective chart review of 857 patients who underwent cardiac catheterization for CHD at UHI from 1st February 2012 to 30th June 2023. Precardiac catheterization clinical data, procedure details, and post-procedure data were recorded. The statistical software SPSS was used for data analysis. We studied 857 patients who underwent cardiac catheterization for CHD at UHI. Females comprised 62.8% (n = 528). The age range was 3days to 64years, with a mean of 5.1years (SD 7.4). Advanced heart failure was present in 24(2.8%) of the study participants. The most common procedures were patent ductus arteriosus device closure (n = 500, 58.3%), diagnostic catheterization (n = 194, 22.5%), and balloon pulmonary valvuloplasty (n = 114, 13.0%). PDA device closure had 89.4% optimal results while BPV had 75.9% optimal performance outcome. Adverse events occurred in 52 out of 857 study participants (6.1%). Clinically meaningful adverse events (CMAES) occurred in 3.9%, (n = 33), high severity adverse events in 2.9% (n = 25) and mortality in 1.5% (n = 13). Advanced heart failure at the time of cardiac catheterization, was significantly associated with clinically meaningful adverse events (OR 52 p-value < 0.001) and mortality (OR 564, p value < 0.001). Many patients with CHD have benefited from the cardiac catheterization program at UHI with high optimal procedure outcome results. Patients with advanced heart failure at the time of cardiac catheterization have less favorable outcomes emphasizing the need for early detection and early intervention.