Objectives: Thoracic sarcomas are a heterogeneous group of rare mesenchymal tumors. This study aimed to identify prognostic factors for overall survival (OS) and progression-free survival (PFS) in patients undergoing resection of primary thoracic soft tissue and bone sarcomas. Methods: We retrospectively reviewed patients with primary intrathoracic or chest wall sarcomas who underwent surgical resection between 2005 and 2020. Eighty-four patients were included: 60 with soft tissue sarcoma and 24 with bone sarcoma. Univariate and multivariate Cox regression analyses were performed to identify prognostic factors for PFS and OS. Results: The most common histological subtypes were chondrosarcoma (19%) and undifferentiated pleomorphic sarcoma (17.8%). Overall, 54.8% of patients were female, and the mean age was 55.7 years (SD 17.9). Neoadjuvant and adjuvant therapies were primarily administered in intermediate- (G2) and high-grade (G3) tumors. Median OS was 28.4 months. On multivariate analysis, high tumor grade (G3 vs. G1–2) independently predicted worse PFS (HR 3.21, 95% CI 1.34–7.68; p = 0.01) and OS (HR 4.40, 95% CI 1.56–12.41; p = 0.01). Larger tumor size (HR 1.09, 95% CI 1.03–1.15; p = 0.001) and incomplete resection (HR 12.21, 95% CI 2.56–58.34; p = 0.002) were independently associated with worse OS, while lung metastases at diagnosis independently predicted worse PFS (HR 4.89, 95% CI 1.21–19.69; p = 0.03). Conclusions: Histological grade is the strongest independent predictor of survival in resected thoracic sarcoma. Surgery alone appears adequate for low-grade sarcomas, whereas multimodal treatment strategies seem particularly relevant for patients with higher-grade sarcomas.