The present study was designed to investigate the current status of mandated treatment in prison for sexual offenders in Taiwan. The information-gathering methods were composed of two parts: questionnaires and interviews. The results showed the difficulties of mandated treatment in prison, including poor client adherence, the lack of consistent disciplines for the therapists, a standardized algorithm, and explicit laws and rules, the safety concerns of the therapists, and a shortage of staff. The development of mandated treatment in prison of sexual offenders in Taiwan is still in its early stage, and the treatment models have not yet been integrated. A cooperative and collaborative center for the mandated treatment in prison of sexual offenders and an integrated rule and treatment model should be set up in the future.