A 76-year-old man developed a painless right-sided abdominal bulge in the T11 dermatome on the right flank 12 days after classical herpes zoster (HZ). HZ is a reactivation of varicella-zoster virus that usually causes unilateral dermatomal vesicles, while deep tissue involvement is rare. Examination revealed a soft swelling without pitting. Computed tomography showed ipsilateral thinning of the abdominal wall muscles without a fascial defect, true hernia, or mass. This finding is consistent with segmental motor neuropathy associated with shingles, which manifests as an abdominal pseudohernia. The patient was treated conservatively without the need for surgery. The case highlights a rare neuromuscular complication of HZ and supports the use of imaging in unexplained abdominal swelling after HZ.