Primary involvement of skeletal muscle by cystic echinococcosis is exceptional, even in endemic regions. We describe a 44-year-old man with no relevant medical history who presented with a progressively enlarging, painful mass of the anteromedial left thigh. The mass was complicated by ipsilateral deep vein thrombosis extending from the femoral vein to the external iliac vein. Magnetic resonance imaging showed a thin-walled, multivesicular, honeycomb-like lesion confined to the muscles of the thigh and measuring 26 × 14 × 8 cm, without bone lysis. Hydatid serology was positive, and screening of the liver and lungs was negative. The cyst was removed en bloc through a direct anterior approach without rupture of its wall, with the surrounding soft tissues protected by drapes soaked in hypertonic saline. Albendazole was given as adjuvant medical treatment. This case illustrates that a large intramuscular cystic mass can compress the deep veins and cause thrombosis, and that careful complete excision combined with albendazole is the cornerstone of management.