Eosinophilic fasciitis (EF) is a rare disease characterized by symmetric and painful swelling with progressive induration and thickening of the skin and soft tissues of the limbs and trunk. Herein, we report a case of a 31-year-old woman who presented with painful swelling in both lower legs which persisted for 6 days. She underwent ultrasonography (US) in an out-patient department to rule out deep-vein thrombosis. The US did, however, reveal perifascial fluid in the thickened superficial fascia and interstitial fluid in the subcutaneous layer of both lower legs. Magnetic resonance imaging findings were identical to the US and additionally showed no involvement of the muscles or deep fascia. Laboratory data, showing peripheral eosinophilia and a US-guided gun-biopsy showing lymphocytic and eosinophilic infiltration were both indicative of EF. The patient was treated with corticosteroids, resulting in a remarkable improvement in both the lower-leg edema and peripheral eosinophilia. There was no recurrence after 7 years of follow-up.