Introduction: The cardinal symptom of herpes zoster (HZ) is pain. However, in rare cases, it may be accompanied by motor paralysis. Avoidance of movement due to pain delays the detection of paralysis and can be difficult to differentiate from disuse and side effects of drugs even after pain relief. We report a case in which the diagnosis of unilateral paralysis on manual muscle testing (MMT) led us to conclude HZ paralysis was more likely rather than disuse or drug side effects. Case Report: A 90-year-old man who presented with rash and stinging pain in his right thigh was diagnosed with HZ. Because he was unable to move his right leg due to pain at onset, pregabalin was prescribed. Although pain was alleviated after 3 weeks, he failed to walk. MMT revealed decreased motor function of the right hip and knee joints, so he was diagnosed with paralysis of the right L2 to L4 due to HZ. Discussion: In cases of suspected paralysis due to HZ, detailed examinations should be conducted for differentiation with other pathologies causing muscle weakness.