This study explored how facilitation skills—defined as instructional techniques that accurately convey core messages in a trusting relationship and encourage self-directed learning participation among adult learners—affect the effectiveness of learning. The research focused on adult learners enrolled in lifelong education programs at seven universities, including general and vocational colleges in Busan. It aimed to examine the relationships between instructors’ facilitation skills, learner engagement, and learning outcomes, as well as the mediating effect of engagement on these relationships. A total of 213 valid survey responses were analyzed from an initial 215 responses, excluding 2 unsuitable entries. The findings are summarized as follows. First, facilitation skills were found to partially influence learner engagement. Second, learner engagement was shown to affect learning outcomes. Third, facilitation skills were found to have a partial effect on learning outcomes. Fourth, learner engagement partially mediated the relationship between facilitation skills and learning outcomes. Based on these results, this study is expected to contribute to a deeper understanding of the relationship between facilitation skills and learning outcomes in adult learners, providing practical guidelines for enhancing effectiveness in various educational contexts.