Although spiritual caregiving is a key domain of palliative care, it lacks a clear definition, which impedes both caregiving and research in this domain. The aim of this study was to conceptualize spirituality by identifying dimensions, based on instruments measuring spirituality in end-of-life populations. A systematic literature review was conducted. Literature published between 1980 and 2009, focussing on instruments measuring spirituality at the end of life was collected from the PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and PsycINFO databases. Inclusion criteria were: (1) the studies provide empirical data collected with an instrument measuring spirituality or aspects of spirituality at the end of life; (2) the data report on a (subgroup) of an end-of-life population, and (3) the instrument is available in the public domain. Content validity was assessed according to a consensus-based method. From the items of the instruments, three investigators independently derived dimensions of spirituality at the end of life. In 36 articles that met the inclusion criteria we identified 24 instruments. Nine instruments with adequate content validity were used to identify dimensions of spirituality. To adequately represent the items of the instruments and to describe the relationships between the dimensions, a model defining spirituality was constructed. The model distinguishes the dimensions of Spiritual Well-being (e.g., peace), Spiritual Cognitive Behavioral Context (Spiritual Beliefs, Spiritual Activities, and Spiritual Relationships), and Spiritual Coping, and also indicates relationships between the dimensions. This model may help researchers to plan studies and to choose appropriate outcomes, and assist caregivers in planning spiritual care.