Purpose Retrograde intrarenal surgery (RIRS) is a safe and effective treatment option for upper urinary tract stones smaller than 2cm. Although several studies have documented perioperative and postoperative complications related to RIRS, there exists limited data regarding the readmission and rehospitalization of patients after RIRS. The aims of the study were to document the rates of readmission and rehospitalization after RIRS and to determine the predictive factors for readmission and rehospitalization. Materials and Methods In this study, we retrospectively analyzed patients who underwent RIRS for the treatment of renal stone disease and were unexpectedly readmitted to the hospital within 30 days after discharge. The hospital admission systems were used to determine readmissions and rehospitalizations. Readmission and rehospitalization rates, causes, and treatment procedures were evaluated. Univariate and multivariate analyses of clinicodemographic properties were performed to evaluate possible predictive factors for readmission and rehospitalization after RIRS. Results A total of 1,036 patients were included in the study. Of these patients, 103 (9.9%) were readmitted to the hospital. Among these readmissions, 35 patients (33.9%) were rehospitalized and 14 (13.6%) underwent surgical intervention. The most common reasons for readmission were renal colic and fever. The presence of preoperative pyuria (odds ratio [OR] 1.86), stone volume (OR 1.54), postoperative complications (OR 3.66), and stone-free status (OR 0.46) were predictive factors for readmission, whereas hospitalization time (OR 1.32), postoperative complications (OR 9.70), and stone-free status (OR 0.06) were predictive factors for rehospitalization after RIRS. Conclusion Nearly 10% of patients who underwent RIRS were readmitted to the hospital within the first month after discharge, and some were rehospitalized. Preoperative pyuria, high stone volume, presence of postoperative complications, and low stone-free status predicted this readmission and rehospitalization. Clinicians must recognize these predictive factors and inform their patients about this possibility.