Background: Pembrolizumab is a humanized IgG4 antibody from the immune-checkpoint inhibitors (ICI) family that has been proven to improve clinical outcomes in many solid organ malignancies. Despite its great therapeutic results, this novel drug has undesirable side effects, including uncommon cardiac and neuromuscular adverse effects. Case presentation: The patient, a known case of hypertension, COPD, HFpEF and NSCLC presented with mild chest pain and shortness of breath on exertion for 5 days. His CT scan revealed no pulmonary emboli. His echocardiogram indicated an EF of 10-15%, worldwide hypokinesis, reduced RV function, and a moderately enlarged left atrium. He underwent coronary angiography, which revealed no obstructive lesions. He was managed with IV Lasix, IV methylprednisolone in hospital and prednisone, furosemide, metoprolol succinate, and lisinopril on discharge. He was prescribed spironolactone at his two-week follow-up. Conclusion: Pembrolizumab-induced cardiomyopathy is uncommon and should be treated with care because there is no cure.