Primary malignant peripheral nerve sheath tumour (MPNST) is an uncommon malignant tumour that arises from the peripheral nerves. Most of these tumours arise in the regions of the trunk, head and neck, or extremities and are rarely seen in the abdomen. In this report, we describe a case of MPNST of the greater omentum, which, to the best of our knowledge, is only the second case reported in the literature. MPNST is an uncommon tumour that can show local invasion and has a high risk of recurrence. We also discuss the utility of "omental vascular pedicle sign" to help establish the omental origin of intra-abdominal masses.