Background and purpose Patients treated with low radiotherapy dose or treated at young age are at a risk of developing local relapse. Although data are preliminary, brachytherapy seems an attractive treatment option for recurrent prostate cancer after previous radiotherapy. Therefore, the UroGEC group of the GEC-ESTRO conducted a Delphi study, to explore expert opinion on the management of salvage prostate brachytherapy. Material and methods For this study, a series of digital questionnaires were sent, which enabled data collection from an international group of experienced participants. Consensus was defined as 80% agreement for each question. Results Eighteen experts completed all rounds of the Delphi study. After the final round consensus was reached on 17 out of 38 (45%) questions. Consensus was reached in 52% of questions about patient selection, in 50% of the questions about diagnostic tests and in 22% of the questions on performing salvage prostate brachytherapy. Conclusions The group was able to find consensus on less than half of the questions. Most consensus was reached on topics involving patient selection and diagnostic tests, where participants could build on their experience of daily practice. However, the way to perform the salvage treatment is less established and results in more disagreement between participants.