Background: Arrythmia is a major cause of cardiovascular morbidity and mortality in patients with congenital heart diseases. It has multifactorial predisposing factor as congenitally malformed or displaced conduction system, hemodynamic, mechanical or hypoxic stress and residual or postoperative sequelae. Methods: This was a prospective observational study involving all patients who were following up or referred to congenital and structural heart disease unit in our department over a period of 42 months and were discovered to have significant symptomatic cardiac arrhythmia. A detailed custom-made sheet was applied to all eligible patients to collect demographic data, underlying congenital heart disease, type of arrhythmia and possible management and/or outcome. Results: The study population included 107 patients with different congenital heart diseases with mean age 20.47+/- 13.2. Bradyarrhythmia were more common (67%) than tachyarrhythmia. Post-operative CHB was the most common bradyarrythmia. One third of the patients had atrial or ventricular tachyarrythmia. Post Fallot repair patients developed ventricular tachycardia while patients with Ebstein anomaly more commonly developed atrial tachycardias, flutter or SVT. Patients with CHB were managed with transvenous pacing (51%), epicardial pacing (16%), two patients with CCTGA with impaired RV functions underwent CRT implantation, two patients post Fallot repair underwent ICD implantation. Conclusion: Patients with CHD are subjected to wide range of arrhythmias. Postoperative complete heart block was the commonest arrhythmia in this registry especially in patients with L-TGA, AVSD and VSD. Tachyarrythmias accounted for one third of the patients. Atriotomy incisions, sutures, and conduit is a major risk factor for post-operative atrial tachycardia. The use of ICDs and CRT in patient with congenital heart diseases have proven relative efficacy.