Background and Objectives: Postoperative readmissions are often used to assess quality of surgical care. This study compared 30-day vs 31-to 90-day readmission following surgery for ovarian, fallopian tube, or primary peritoneal cancer. Methods: This retrospective study of the 2010-2015 Nationwide Readmissions Database characterized 90-day readmissions following cytoreductive surgery for these cancers. Each patient's first postoperative hospitalization was included. Univariate analysis compared patient demographics and reasons for readmission. Multivariable regression identified independent predictors of readmission. Results: Of an estimated 76 652 patients, 10 264 (13.4%) were readmitted within 30 days, and 6942 (9.1%) between 31 and 90 days. The 30-day readmissions were more frequently associated with postoperative infection, while 31-to 90-day readmissions were more frequently associated with renal or hematologic diagnoses.