Background: Dengue fever may cause cardiac manifestations, including transient electrocardiographic (ECG) abnormalities. Atrioventricular (AV) conduction disturbances are rarely reported in children. Case Report: An 8-year-old boy with dengue fever and thrombocytopenia presented with an irregular cardiac rhythm. ECG revealed AV conduction delay, intermittent Mobitz type I second-degree AV block, and junctional rhythm. He remained hemodynamically stable and was managed conservatively with serial ECG monitoring. The abnormalities progressively resolved by day 4, and follow-up at 6 months showed normal sinus rhythm without residual conduction defects. Conclusion: Dengue fever may cause transient AV conduction abnormalities in children. This case highlights the importance of ECG assessment and serial monitoring to identify cardiac involvement and document recovery.