BACKGROUND The severe iatrogenic hypogonadal state induced by medical castration used for treatment of prostate cancer is associated with adverse effects including fatigue, increased fracture risk, and a decrease in skeletal muscle function, which negatively impact quality of life. We have previously reported beneficial changes in healthy lifestyle behaviors, physical function and fatigue as a result of a novel combined exercise and dietary advice intervention (a lifestyle intervention) in men with prostate cancer on androgen suppression therapy (AST). The aim of this research was to conduct a qualitative evaluation of the lifestyle intervention in these men with advanced prostate cancer receiving androgen suppression therapy (AST). METHODS Twelve men with prostate cancer on AST took part in three focus groups in a UK higher education institution following the 12 week intervention. Sessions lasted between 45 and 60 minutes in duration. All discussions were audio-taped and transcribed. A framework analysis approach was applied to the focus group data. An initial coding framework was developed from a priori issues listed in the topic guide and extended and refined following initial familiarization with the focus group transcripts. Line by line indexing of the transcripts was undertaken iteratively to allow for the incorporation of new codes. Coded sections of text were grouped together (charted) into themes and subthemes prior to a further process of comparison and interpretation. RESULTS None of the participants involved in the trial were provided with information on how lifestyle changes might be beneficial to men with prostate cancer during the course of their standard medical treatment. We present novel findings that this intervention was considered beneficial for reducing anxiety around treatment and fear of disease progression. Men were supportive of the benefits of the intervention over conventional cancer survival discussion group arrangements as it facilitated peer support in addition to physical rehabilitation. CONCLUSIONS The benefits of lifestyle changes in men with prostate cancer are not well appreciated by care providers despite a range of benefits becoming apparent. Strategies to implement exercise and dietary interventions in standard care should be further evaluated. TRIAL REGISTRATION Current Controlled Trials ISRCTN88605738.