Reports show that selective internal radiation therapy (SIRT) may downsize inoperable liver tumors to resection or transplantation, or enable a bridge-to-transplant. A small-cohort study found that long-term survival in patients undergoing resection following SIRT appears possible but no robust studies on postsurgical safety outcomes exist. The Post-SIR-Spheres Surgery Study was an international, multicenter, retrospective study to assess safety outcomes of liver resection or transplantation following SIRT with yttrium-90 (Y-90) resin microspheres (SIR-Spheres®; Sirtex). Data were captured retrospectively at participating SIRT centers, with Y-90 resin microspheres, surgery (resection or transplantation), and follow-up for all eligible patients. Primary endpoints were perioperative and 90-day postoperative morbidity and mortality. Standard statistical methods were used. The study included 100 patients [hepatocellular carcinoma: 49; metastatic colorectal cancer (mCRC): 30; cholangiocarcinoma, metastatic neuroendocrine tumor, other: 7 each]; 36% of patients had one or more lines of chemotherapy pre-SIRT. Sixty-three percent of patients had comorbidities, including hypertension (44%), diabetes (26%), and cardiopathy (16%). Post-SIRT, 71 patients were resected and 29 received a liver transplant. Grade 3+ peri/postoperative complications and any grade of liver failure were experienced by 24 and 7% of patients, respectively. Four patients died <90 days postsurgery; all were trisectionectomies (mCRC: 3; cholangiocarcinoma: 1) and typically had one or more previous chemotherapy lines and presurgical comorbidities. In 100 patients undergoing liver surgery after receiving SIRT, mortality and complication rates appeared acceptable given the risk profile of the recruited patients.