Background: Small-bowel obstruction (SBO) after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS/HIPEC) is a common complication associated with re-admission that may alter patients’ outcomes. Our aim was to characterize and investigate the impact of bowel obstruction on patients’ prognosis. Methods: This was a retrospective analysis of patients with SBO after CRS/HIPEC (n = 392). We analyzed patients’ demographics, operative and perioperative details, SBO re-admission data, and long-term oncological outcomes. Results: Out of 366 patients, 73 (19.9%) were re-admitted with SBO. The cause was adhesive in 42 (57.5%) and malignant (MBO) in 31 (42.5%). The median time to obstruction was 7.7 months (range, 0.5–60.9). Surgical intervention was required in 21/73 (28.7%) patients. Obstruction eventually resolved (spontaneous or by surgical intervention) in 56/73 (76.7%) patients. Univariant analysis identified intraperitoneal chemotherapy agents: mitomycin C (MMC) (HR 3.2, p = 0.003), cisplatin (HR 0.3, p = 0.03), and doxorubicin (HR 0.25, p = 0.018) to be associated with obstruction-free survival (OFS). Postoperative complications such as surgical site infection (SSI), (HR 2.2, p = 0.001) and collection (HR 2.07, p = 0.015) were associated with worse OFS. Multivariate analysis maintained MMC (HR 2.9, p = 0.006), SSI (HR 1.19, p = 0.001), and intra-abdominal collection (HR 2.19, p = 0.009) as independently associated with OFS. While disease-free survival was similar between the groups, overall survival (OS) was better in the non-obstruction group compared with the obstruction group (p = 0.03). Conclusions: SBO after CRS/HIPEC is common and complex in management. Although conservative management was successful in most patients, surgery was required more frequently in patients with MBO. Patients with SBO demonstrate decreased survival.