This article focuses on the discussion of the concept of Ronggowarsito's Islamic theosophy in Serat Sabdajati with the purpose to identify the concept in detail. The data of this study were obtained mainly from Serat Sabdajati, which were analyzed through text analysis techniques—carried out with a structural analysis approach. The results showed that Serat Sabdajati contains several Islamic theosophical values. The values contained in include the value of Aqeedah (Islamic doctrine) and Akhlaq (Ethics in Islam). The Value of the Aqeedah consists of the Advice to be close to God, the Advice to Believe in God's Atonement, and the Prohibition to believe another God. Meanwhile, the value of Akhlaq consists of the Teaching of humbleness, Self-Reliance and Introspection, and the Teaching of Patience.