Hereditary neuropathy with liability to pressure palsies (HNPP) is characterized by acute, painless, and recurrent mononeuropathies that are secondary to compression or minor trauma. This case is the first to report an intraspinal compression of the radicular nerve by schwannoma in a patient with HNPP. A 66-year-old woman developed left foot drop and paresthesia of the lateral aspects of left distal lower leg. An electromyography showed left L5 radiculopathy and severe peripheral polyneuropathy. A lumbosacral magnetic resonance imaging revealed a radicular nerve in the intradural and extramedullary space being compressed by schwannoma. She previously had symptoms of foot drop several years ago, and HNPP was confirmed by peripheral myelin protein 22 deletion. She was surgically treated for L5 radiculopathy, which might have been caused by a traction of the nerve root by schwannoma at the intradural and extramedullary space. After surgical treatment, her symptoms of foot drop had improved from zero grade to IV+ grade within 4 weeks. The occurrence of HNPP and schwannoma in the same patient may be coincidental, but it is tempting to speculate that they share a common genetic basis. Therefore, for patients with HNPP, it is important to consider not only an electrophysiologic study but also a magnetic resonance imaging to locate the exact pathologic site.