BACKGROUND Apical hypertrophic cardiomyopathy (ApHCM), also known as Yamaguchi syndrome, is a rare variant of hypertrophic cardiomyopathy characterized by the thickening of the left ventricle apex (>15 mm) and giant negative T-waves on the precordial leads of the electrocardiogram (ECG), which can present symptoms and electrocardiographic changes that mimic acute coronary syndrome (ACS). This report describes the case of a 46-year-old man with chest pain and giant T-wave inversion on ECG, requiring multimodal cardiac imaging to diagnose ApHCM (Yamaguchi syndrome) and exclude the diagnosis of coronary artery occlusion and myocardial infarction. CASE REPORT We report the case of a 46-year-old man who presented to the Emergency Department with typical chest pain. His ECG revealed significant alterations highly suggestive of ACS, including ST-segment depression and giant negative T-waves (>10 mm) in leads V4-V6. Despite this presentation, serial high-sensitivity troponin levels remained consistently within the normal range. Coronary computed tomography angiography (CCTA) revealed non-obstructive coronary arteries but indicated increased apical left ventricular (LV) wall thickness with characteristic trabeculation, raising suspicion for ApHCM. Transthoracic echocardiography (TTE) confirmed pronounced apical LV thickening (20 mm) and a reduced Global Longitudinal Strain (GLS) of -14.3%. Cardiac magnetic resonance (CMR) imaging provided a definitive diagnosis, identifying significant apical hypertrophy with systolic obliteration of the LV cavity and quantifying multifocal myocardial fibrosis at 6% of the LV mass. The patient's symptoms improved significantly with medical therapy, including losartan, metoprolol, and trimetazidine. CONCLUSIONS This case highlights the critical diagnostic challenge of ApHCM masquerading as ACS. It underscores the indispensable role of a multimodal imaging approach-integrating ECG, TTE, CCTA, and CMR-for an accurate diagnosis, particularly for identifying underlying myocardial fibrosis and guiding appropriate patient management.