Multiple myeloma, also known as myeloma or plasma cell myeloma, is a progressive hematologic disease. Complications of multiple myeloma include renal insufficiency, hematologic complications (anemia, bone marrow failure, bleeding disorders), infections, bone complications (pathologic fractures, spinal cord compression, hyercalcemia), and neurologic complications (spinal cord and nerve root compression, intracranial plasmacytomas, leptomeningeal involvement, among others). This article reviews these various complications connected to multiple myeloma, examining their various causes and possible treatment.