There is a growing body of research on the effectiveness of rehabilitation programs in a Young Offenders' Institution (YOI). The aim of the present study is to investigate the effectiveness of rugby training as a rehabilitation intervention in a YOI in the United Kingdom. Young adult males (n=46) currently serving sentences at the YOI were split into two groups, intervention (n=25; mean age, 19.64±0.81 years) and no intervention (n=21; mean age, 19.76±0.89). Participants completed the Criminal Attitudes and Associates (MCAA) instrument at three different time cycles and then pre/post for intervention group. Additionally, qualitative interviews (one to one and focus groups) were carried out with the intervention and no intervention groups during the same cycles of the study. The results of questionnaire analysis showed no significant difference in MCAA measures taken before and after rugby intervention. Interestingly, the intervention group showed more procriminal attitudes on their responses compared to the no intervention group. Finally, analysis of the 3 cycles of data collected showed that the time of the year the questionnaire was completed has a significant impact on the responses given. In contrast, the qualitative interviews showed a very positive change of attitude towards rehabilitation from the intervention group after rugby training. The implications of the results in relation to studies aimed at evaluation of the intervention programs in YOI are discussed.