Background: Malignant phyllodes (MP) and primary breast sarcomas (PBS) are rare neoplasms with overlapping histopathologic features. We compared overall survival (OS) and estimated the association of surgery and therapies with OS. Methods: We utilized the National Cancer Database (2004–2016). Patients without surgery, unknown surgery, or margins, or Stage IV disease were excluded. Kaplan–Meier curves and Cox proportional hazards models were used to estimate unadjusted and adjusted OS, respectively. Results: A total of 3209 (59.5%) MP, and 2185 (40.5%) PBS were identified. Despite a larger median tumor size in MP (46 vs. 40 mm PBS, p < 0.001), lumpectomy rate was higher for MP (52.9% vs. 27.0% PBS, p < 0.001). Compared to MP, PBS patients more frequently received radiation (28.9% vs. 24%), and chemotherapy (28.1% vs. 4%), both p < 0.001. Unadjusted OS was lower for PBS (57% vs. 85% MP, log-rank p < 0.001). PBS (vs. MP) had persistently worse survival (hazard ratio [HR]: 1.98, 95% confidence interval [CI]: 1.69–2.31) after adjustment. Receipt of adjuvant therapies was not associated with OS (either neoplasm); however, lumpectomy was associated with improved OS (vs. mastectomy) for both PBS (HR: 0.59, 95% CI: 0.50–0.75) and MP (HR: 0.65, 95% CI: 0.53–0.81). Positive margins had no association with OS for MP (HR: 1.09, 95% CI: 0.75–1.60), but was associated with worse survival for PBS (HR: 2.35, 95% CI: 1.82–3.02). Discussion: We found significant survival differences between MP and PBS, with PBS having a consistently worse OS. Our findings support surgery as the mainstay of treatment for both tumor types and suggest that lumpectomy may be a reasonable option for select patients without compromising outcomes.