Background: Radical gastrectomy is the cornerstone of the treatment of locally advanced gastric cancer. This study was designed to evaluate factors associated with a tumor-positive resection margin after gastrectomy and to evaluate the influence of hospital volume. Methods: In this Dutch cohort study, patients with junctional or gastric cancer who underwent curative gastrectomy between 2011 and 2017 were included. The primary outcome was incomplete tumor removal after the operation defined as the microscopic presence of tumor cells at the resection margin. The association of patient and disease characteristics with incomplete tumor removal was tested with multivariable regression analysis. The association of annual hospital volume with incomplete tumor removal was tested and adjusted for the patient- and disease characteristics. Results: In total, 2799 patients were included. Incomplete tumor removal was seen in 265 (9.5%) patients. Factors associated with incomplete tumor removal were: tumor located in the entire stomach (odds ratio (OR) [95% confidence interval (CI): 3.38 [1.91–5.96] reference: gastroesophageal junction), cT3, cT4, cTx (1.75 [1.20–2.56], 2.63 [1.47–4.70], 1.60 [1.03–2.48], reference: cT0-2), pN+ (2.73 [1.96–3.80], reference: pN−), and diffuse and unknown histological subtype (3.15 [2.14–4.46] and 2.05 [1.34–3.13], reference: intestinal). Unknown differentiation grade was associated with complete tumor removal (0.50 [0.30–0.83], reference: poor/undifferentiated). Compared with a hospital volume of < 20 resections/year, 20–39, and > 39 resections were associated with lower probability for incomplete tumor removal (OR 0.56 [0.42–0.76] and 0.34 [0.18–0.64]). Conclusions: Tumor location, cT, pN, histological subtype, and tumor differentiation are associated with incomplete tumor removal. The association of incomplete tumor removal with an annual hospital volume of < 20 resections may underline the need for further centralization of gastric cancer care in the Netherlands.