Bipolar I disorder is characterized by the presence of at least one manic episode (DSM-5). Despite a decent percentage of individuals being diagnosed later in life, there currently exist no formal treatment guidelines for late-onset bipolar disorder (LOBD), which remains poorly understood. Typically, manic or manic-like episodes in elderly individuals can be thought of as arising from a secondary, physical cause. However, in the absence of a pre-existing neurological disorder - and when laboratory, imaging, and exam findings do not fully support a neurological picture - the determination of a structural versus primary etiology for LOBD becomes challenging.We present the case of Ms. S, a 79-year-old woman with a past psychiatry history of bipolar disorder diagnosed after 2012 and non-contributory past medical history who was admitted to a state mental hospital on a probate court order from local jail secondary to labile mood and physical aggression toward an officer. Initial labs were remarkable for slightly elevated low-density lipoprotein and a B12 at the lower limit of normal. She was started on a regiment oral B12 supplement, valproic acid 500 mg twice daily, haloperidol 5 mg nightly, and diphenhydramine 25 mg nightly. Despite her medication regimen, she continued to display marked mood lability, tangential thought processes, grandiose delusions, and paranoia. A CT head one week into admission revealed bilateral periventricular white-matter hyperintensities with decreased attenuation and chronic white-matter infarcts. She underwent five sessions of electroconvulsive therapy (ECT), with significantly improving Montreal Cognitive Assessment and Young Mania Rating Scale scores. At the time of discharge on day 32, the patient was fully oriented to self and surroundings with good hygiene, a normal rate of speech, euthymic mood, and congruent affect.The case of Ms. S underscores the importance of a thorough workup to rule out secondary causes of mania. In addition, it is a clarion call for revisiting and researching a comprehensive management approach to LOBD, for which serial cognitive assessments and ECTs may play an important role.