This study examined how raters' feedback characteristics affect ratees' feedback acceptance and development motivation as a post-acceptance outcome in a multi-source feedback context. Additionally, it sought to determine whether the relationship between feedback acceptance and development motivation differs according to individual levels of self-efficacy. For the empirical analysis, 25 publicly listed Korean companies that had adopted multi-source feedback systems and were providing substantive feedback for employee development were analyzed. The results confirmed that feedback characteristics are a major predictor of feedback acceptance, and that feedback acceptance subsequently influences the formation of development motivation. Specifically, first, regarding feedback characteristic factors, feedback acceptance was found to increase when the feedback content was described in specific terms, consisted of information valuable for one's future job performance, and was positive in nature. Second, feedback acceptance was found to have a positive correlation with self-development motivation as a subsequent psychological outcome. Finally, despite the theoretical link between self-efficacy and development motivation, the moderating effect of self-efficacy as an individual difference variable on the relationship between feedback acceptance and development motivation was not confirmed in this study.