<p>Multiple myeloma (MM) is the second most common hematological malignancy and the leading primary malignancy involving the adult spine. Spinal involvement often results in pathological fractures, neurological compromise, or mechanical instability, making surgical stabilization necessary before radiotherapy. This study sought to analyze the functional outcomes of posterior spinal instrumentation in MM patients. We retrospectively reviewed all MM patients who underwent posterior spinal instrumentation for spinal instability at our institution between January 2016 and July 2023. Surgical candidacy was determined using Spinal Instability Neoplastic Score (SINS) criteria. Thirty patients met the inclusion criteria. Data included demographics, comorbidities, ASA class, baseline function, surgical details, and perioperative outcomes. Preoperative labs, were analyzed for associations with complications and hospital stay. The mean age was 56.77 ± 10.07 years, with 63.33% male. The mean follow-up was 39.63 months. There were 6 readmissions (20%), 3 mortalities (10%), and 2 reoperations (6.67%). Postoperatively, 23 patients (76.7%) demonstrated functional improvement with independence improving from 3.33% preoperatively to 53.33% postoperatively. Four patients (13.33%) underwent minimally invasive fixation, while 26 (86.67%) underwent open instrumentation. Single-level involvement was observed in 25 patients (83.33%), with multilevel disease in 5. Complications occurred in 20% of patients, most commonly wound infection, and no instrumentation failures were recorded. IgG kappa was the predominant myeloma subtype (40%). Posterior instrumentation for MM-related spinal instability is safe and effective, providing significant functional gains. Hypoalbuminemia was common but not predictive of prolonged hospitalization, indicating that low albumin alone should not preclude surgical stabilization.</p>