Abstract Voluntary organizations as well as churches rely heavily on Christian volunteers, yet research on their motivation delivers conflicting answers and limited guidance. This paper applies a comprehensive (2,485 records screened) scoping review-based approach mapping 79 empirical studies (1989–2026) on Christian volunteer motivation across church and civil society projects. Using the UN Volunteers 2020 framework, we analyze (i) study designs, theoretical lenses, instruments, (ii) volunteer populations, and (iii) project settings. We identify three structural barriers to cumulative knowledge: heterogeneous and often implicit motivation concepts; an instrument–phenomenon mismatch that sidelines religious motives (notably through uncritical reliance on the Volunteer Functions Inventory); and systematic underreporting of key participant and context variables. These gaps account for much of the contradictory evidence and restrict its practical use. We outline concrete reporting and measurement standards to integrate religious motives into mainstream volunteering research and to improve evidence-informed management of Christian volunteers.
Fröh et al. (Thu,) studied this question.