INTRODUCTION: Froin syndrome is a rare condition that is defined as marked coagulability, elevated protein level, and xanthochromia of the cerebrospinal fluid (CSF). Froin syndrome more commonly occurs because of obstruction of CSF flow due to underlying inflammatory or neoplastic conditions. CASE REPORT: We present a case of a 38-year-old man who was found to have Froin syndrome a year after he was diagnosed with multiple myeloma (MM). CSF analysis, laboratory work-up, and magnetic resonance imaging of the neuroaxis supported the diagnosis of Froin syndrome related to leptomeningeal myelomatosis. To our knowledge, this is the first reported case of FS due to MM. CONCLUSION: Leptomeningeal myelomatosis associated with MM can cause blockage of CSF circulation leading to Froin syndrome. Inflammatory or neoplastic conditions should be considered as an underlying etiology.