Purpose The aim of this retrospective study was to evaluate the tolerance and early as well as late toxicity of high dose rate brachytherapy (HDRBT) boost combined with interstitial hyperthermia (IHT) in patients treated for prostate cancer. Material and methods Between January 2011 and June 2013 76 patients diagnosed with prostate cancer received treatment consisting of external beam radiotherapy (EBRT), followed by a HDRBT boost combined with IHT. IHT was performed before each brachytherapy fraction. Results The median follow-up time was 26.3 months (range 7-43 months). Early genitourinary (GU) grade 1 and 2 toxicities were common, but only two patients (2.6%) experienced acute urinary retention requiring temporary catheterisation (grade 2 toxicity). No grade 3 or 4 genitourinary or gastrointestinal toxicities were observed. In the group analysed, 59 of 76 patients had follow-up times longer than 18 months. The incidence of grade 2 late toxicity in the group studied did not exceed 23.7%. There were no late grade 2 or higher complications from the gastrointestinal tract. Conclusions The tolerance of HDRBT boost combined with IHT is good. The profile and the percentage of early and late complications are acceptable.