ObjectiveExposure based large-group one-session treatments (LG-OSTs) proved feasible in different situational fears and showed promising short- and long-term outcomes. Based on prior LG-OST protocols we explored feasibility and effectiveness of an LG-OST protocol in four cohorts of individuals highly fearful of heights (N = 104). Moreover, we aimed to identify predictors of LG-OST outcome in order to provide individualized treatment recommendations in the future.MethodsParticipants’ fear of heights was assessed at pre- and post-treatment as well as at 5 months follow-up using questionnaires and a behavioral approach test (BAT). Pre-treatment indices of negative emotional traits and positive mental health, the extent by which fear-evoking expectancies were violated during exposure, and post-treatment group perception processes were assessed in order to predict the outcome.ResultsThe LG-OST procedure proved feasible and effective in terms of both subjective and behavioral fear of heights. Post-treatment effects sizes of questionnaires assessing fear of heights ranged between d = 0.94 – 1.43. After the treatment, about half of the participants (49.5%) were able to ascend an aerial fire ladder up to a maximum of 30 m (vs. pre-treatment 17.3%). Follow up results showed the long-term stability of effects. Among psychological constructs, positive mental health and expectancy violation were the strongest predictors of LG-OST long-term outcome.ConclusionWe conclude that exposure based LG-OSTs are feasible, effective and very efficient compared to individual face-to-face settings. Thus, they represent very promising treatment alternatives for situational fears including fear of heights. Moreover, clinical research may benefit from LG-OST protocols as its high standardization may facilitate the search for mediators and moderators of exposure outcomes.