Abstract Background The rarity of Ewing sarcoma of rib has resulted in paucity of data, particularly on the prognostic factors and pattern of relapses. We analyzed the recurrences in patients with primary nonmetastatic Ewing sarcoma of the rib and examined prognostic factors of poor outcome. Methods From January 2004 to January 2011, 37 patients were treated. After induction chemotherapy, complete (from costal cartilage to vertebra) or partial excision of involved rib with or without adjacent ribs was performed. Postoperative radiotherapy was administered for positive margins, poor response to chemotherapy, and large primary tumors with significant soft tissue component at presentation. Results Disease relapsed in 16 patients: at the local site (n = 5), both local and distant (n = 2), and distant site only (n = 9). The projected 5-year cause-specific, relapse-free survival and local control were 50%, 44%, and 72%. Poor response to chemotherapy (>5% residual tumor) and resection of adjacent lung parenchyma (a surrogate for tumor extension) were adverse prognostic factors for relapse-free survival in multivariate analysis. Conclusion Relapses occurred more often at distant sites and had a poor outcome. In this study, poor histologic response to chemotherapy (P = .04) and the infiltration of adjacent lung parenchyma (P = .01) are adverse prognostic factors.