The research was done to describe the Rehabilitation of Mentally Retardation Institution (BBRSBG) Kartini, in Temanggung giving service to mentally retardation. The education at BBRSBG is given especially to beneficiaries suffering from mental retardation. Informants determined purposively to those as the family of beneficiaries, Institution officials, and religious (Islam) teacher. Data gathered through depth interview, observation, and focus group discussion. Data analyzed through qualitative descriptive technique. The tinding showed that religious service at BBRSBG Kartini has yet optimal. Some the beneficiaries have not yet know, understand, and perform religion reffering to AI Quran. Benehciaries have been yet independent to perform the religion as they believe and lack of teacher and mental guides (in Islam) at BBRSBG, only one person. The men responsible for the program do not give enough motivation to rooms and cottages guides. Based on the conclusion, it is recommended that BBRSBG Kartini should add instructure in Islam religion; Replacementof cottages guides with the same faith with the beneficiaries and those guided; The development of religious knowledge should be implemented to the beneficiaries involving rooms guides; Room and cottages guides should increase creativity on their guidance and using method that suite beneficiaries potentiality. The management should increase and enhance good relation and unite perception among Islam and class teachers, and room/cottages guides. The men responsible for program should monitor and evaluate the implementation of guidance and empowerment at rooms/cottages. The manager of the institution should add supporting devices for effectiveness and running well on Islam mental guidance.