We conceptualize supporter loyalty, evaluate a scale for its measurement, and examine which organizational facets are most suitable to serve as loyalty objects. We conducted a survey-based research (N = 306) to examine the influence of supporter loyalty on donation behaviors (four types), volunteering behaviors (three types), organizational citizenship behaviors (four types), and bequest intentions. The effect of supporter loyalty was significant for one type of donation behaviors, all three volunteering behaviors, three of four organizational citizenship behaviors, and bequest intentions. Evaluating the effect sizes indicates that the strength of supporter loyalty’s influence is relatively modest. The organization’s mission and the people served by the organization were the most important loyalty objects.