The issues related to the sexuality of the people with developmental disorders are many because a low level of intellectual function and sociality do not equate to a low level of sexual curiosity and sexual desire. This study aimed to review the evaluation and treatment through a forensic psychiatric evaluation case of sexual offenders with developmental disorders. An assessment of sex offenders with developmental disorders should be comprehensive. The risk of recidivism, cognitive distortion about sex, impulsivity, and comorbid psychiatric disorders should be included. Some therapeutic programs have been developed, and they exhibited the effect through the decreased rate of recurrence of sexual offenses. Therefore, it is necessary to pay more attention to the development of therapeutic programs of sexual offenders with developmental disorder.