The purpose of this study was to examine the relationship between organizational and task factors and the effectiveness of two types of informal learning: peer interaction and learning by doing via own task. The data examined were secondary data derived from the Human Capital Corporate Panel data in 2007, organized and collected by the Korea Research Institute of Vocational Education and Skill Training (KRIVET). A hierarchical multi-regression analysis was applied to data in this study. Study results supported the belief that top management leadership in human resource development (HRD) as well as open communications positively affected the effectiveness of informal learning. However, innovation culture did not have a statistically significant relationship with the effectiveness of informal learning. Further, this study showed that new task and task satisfaction positively influenced this effectiveness. Effectiveness increased when employees recognized that knowledge and skills obtained from current tasks were also useful to other organizations. Implications for practice and recommendations for further research are discussed.