Pharmacotherapy is generally the first choice for the treatment of acute mania in bipolar disorder. Electroconvulsive therapy (ECT) is reported to be an effective treatment modality for mania; however, it is usually used as the “last resort.” Herein, we report a case of a patient with treatment-resistant severe mania in bipolar disorder who recovered with ECT without concurrent antipsychotics and mood stabilizers. Our case report showed that ECT monotherapy can be an effective treatment modality for manic state in bipolar disorder, which may lead to a shorter hospital stay and better social outcomes.