BACKGROUND: Chaplains are increasingly seen as key members of interdisciplinary palliative care teams, yet the specific interventions and hoped for outcomes of their work are poorly understood. This project served to develop a standard terminology inventory for the chaplaincy field, to be called the chaplaincy taxonomy. METHODS: The research team used a mixed methods approach to generate, evaluate and validate items for the taxonomy. We conducted a literature review, retrospective chart review, focus groups, self-observation, experience sampling, concept mapping, and reliability testing. Chaplaincy activities focused primarily on palliative care in an intensive care unit setting in order to capture a broad cross section of chaplaincy activities. RESULTS: Literature and chart review resulted in 438 taxonomy items for testing. Chaplain focus groups generated an additional 100 items and removed 421 items as duplications. Self-Observation, Experience Sampling and Concept Mapping provided validity that the taxonomy items were actual activities that chaplains perform in their spiritual care. Inter-rater reliability for chaplains to identify taxonomy items from vignettes was 0.903. CONCLUSIONS: The 100 item chaplaincy taxonomy provides a strong foundation for a normative inventory of chaplaincy activities and outcomes. A deliberative process is proposed to further expand and refine the taxonomy to create a standard terminological inventory for the field of chaplaincy. A standard terminology could improve the ways inter-disciplinary palliative care teams communicate about chaplaincy activities and outcomes.