Purpose To investigate rates and causes of 30-day readmission for patients who undergo percutaneous transhepatic biliary drainage (PTBD) procedures. Materials and Methods In this retrospective study, PTBD procedures performed at a tertiary care institution (June 2008 to May 2013) were reviewed. For each patient, the first 30-day readmission was used to determine cause of readmission. Two interventional radiologists independently categorized causes for readmission as planned or unplanned, and unplanned causes as related to or unrelated to interventional radiology. Interventional radiology-related readmissions were categorized as potentially preventable or unpreventable. Factors associated with higher odds for 30-day readmission were identified with univariable and multivariable analysis. Results There were 266 procedures in 266 patients (mean age, 67 years; interquartile range, 57-76 years; 53.4% men). The cause of obstruction was malignant in 50.0% of patients (133 of 266). There were 122 of 266 patients (45.9%) readmitted within 30 days. Of these readmissions, 44 of 122 (36.1%) were planned and 78 of 122 (63.9%) were unplanned. A majority of unplanned readmissions (57 of 78; 73%) were related to interventional radiology. Of unplanned interventional radiology-related readmissions, 16% (nine of 57) were related to periprocedural complications and 51% (29 of 57) were considered preventable. At multivariable analysis, Medicaid insurance (odds ratio, 3.68; 95% confidence interval: 1.52, 9.99; P = .009) and bilateral PTBDs (odds ratio, 5.81; 95% confidence interval: 1.79, 18.90; P = .003) were associated with 30-day readmission. Conclusion Thirty-day readmissions after primary biliary drainage are common and a majority of unplanned readmissions are drain-related. Nearly half of unplanned interventional radiology-related readmissions are potentially preventable. © RSNA, 2018 See also the editorial by Nikolic in this issue.