Ewing sarcoma of the pelvis represents a challenging condition because of its aggressive nature and the complexity of achieving adequate oncological resection while preserving limb function. We report the case of a 20-year-old man diagnosed with a localized Ewing sarcoma involving the acetabulum and the periacetabular region. Following neoadjuvant chemotherapy according to the VDC-IE protocol, the patient underwent limb-salvage surgery consisting of an Enneking Type II–III pelvic resection and reconstruction using an iliofemoral stemmed acetabular prosthesis (ice-cream cone prosthesis). Histopathological examination of the resected specimen revealed a poor histological response to neoadjuvant chemotherapy (Huvos grade I) and microscopic residual disease at the surgical margin (R1 resection). Adjuvant radiotherapy and chemotherapy were subsequently administered. The postoperative course was initially uneventful, with satisfactory early functional recovery. During follow-up, the patient developed a pelvic lymphocele, vincristine-induced peripheral neuropathy, and bone metastases eight months after surgery. Despite further oncological management, the disease progressed, and the patient died 12 months postoperatively. This case highlights the feasibility of reconstruction with an ice-cream cone prosthesis following periacetabular resection while emphasizing the prognostic impact of poor histological response and inadequate surgical margins in pelvic Ewing sarcoma.