The issue of religiosity and spirituality and their measurement are quite well developed fields in the psychology of religion. However, the literature shows a lack of research tools to measure the religious experience of the feeling of abandonment by God among followers of the Catholic religion. The purpose of this article is to fulfill this gap through the presentation of the notion of ‘God abandonment’, and its operationalization, by constructing the Scale of Abandonment by God: SAG (Skala Opuszczenia Przez Boga—SOPB). The psychometric value of the tool was evaluated, that is the reliability and validity. In order to achieve this goal, three stages of instrument development (item generation, scale development, and instrument testing) were undertaken in three studies. Stage 1: The pilot study concerned the development of positive statements about the concept of the Catholic experience of God (i.e., the subjective feeling of the experience of God's abandonment in the life of a contemporary person, as well as showing to what extent this belief can affect some aspects of his/her life). Stage 2: Was designed to perform exploratory factor analysis and test–retest reliability to assess stability of the SAG in a three-week time range. Stage 3: Validation of the SAG by Confirmatory Factor Analysis was performed. Result: The SAG can be recognized as a one-factor measure of the feeling of abandonment by God. Because the content of the SAG items indicate the positive aspects of the abandonment of God, this can assist people living in Catholic societies.