Lumbar hernia is a rare condition in which intra or extraperitoneal tissue protrudes through a defect in the posterolateral region of the flank. Incarceration is uncommon but represents a surgical emergency when present. A 54-year-old-male presented to the ED after sudden onset left flank pain after coughing. He was in significant distress secondary to pain and vomiting, and his physical exam revealed a tender mass in his left lateral lumbar region near the site of a previous stab wound. Bedside ultrasound revealed a fluid-filled structure, and CT scan demonstrated herniation of small bowel though the inferior lumbar triangle with associated small bowel obstruction. The patient underwent emergent surgical reduction with mesh repair and recovered uneventfully. Incarcerated lumbar hernia represents a rare diagnosis that may not be at the forefront of most practitioners' differential diagnoses. CT scan is useful to distinguish hernia from solid mass, abscess, or other pathology, while bedside ultrasound may prompt an attempt at immediate reduction. The presence of incarcerated bowel or obstruction warrants immediate surgical consultation.