This research effort empirically tests three factors hypothesized to affect Indonesian millennials’ predisposition to engage in ecotourism experiences, namely universalism value, horizontal collectivism and user generated content (UGC). Indonesia is generally considered a collectivist (as opposed to individualistic) society, yet there is variance in both universalism value and horizontal collectivism. Two studies were conducted, one at ‘soft’, and another at ‘hard’ ecotourism sites. Findings showed that universalism value is positively related to ecotourism predisposition. UGC has a marginal moderating effect on the universalism → ecotourism predisposition. Horizontal collectivism also has a marginal moderating effect on the universalism → ecotourism predisposition in soft ecotourism but has significant effect in hard ecotourism. Both have direct effects on ecotourism predispositions. Managers must recognize that millennials can be segmented based on both universalism value and horizontal collectivism; and that to appeal to those with higher levels on these value dimensions UGC should be encouraged.