The purpose of this study was to investigate the influences of formal learning, personal characteristics, and work environment characteristics on informal learning among middle managers in the Korean banking sector. The conceptual framework identified three factors influencing informal learning. For this study, data collection was conducted in the Korean Banking Institute (KBI) to prepare employees who were working in the banking sector which has been characterized as one of the fastest changing industries in Korea. Thus, middle managers as a population were selected due to their various experiences in both formal and informal learning. The collected data was analyzed using structural equation modeling, correlation analysis, descriptive analysis, and thematic analysis to answer seven research questions. The results of this study showed that the conceptual model representing three factors as influencing factors on informal learning reasonably fit the data from middle managers with a slightly modified structural equation model. Based on the modified model, the results were: (1) formal learning significantly affects informal learning, (2) personal characteristics significantly affect informal learning, (3) work environments do not directly affect informal learning, but they indirectly affect through formal learning, and (4) both personal and work environment characteristics affect formal learning. The results also showed that middle managers engage in various informal learning, even though self-experimentation is the most frequently used type of the three types of informal learning. The consequences resulting from engaging in informal learning were the acquisition of work-related knowledge and skills, individual development, and the development of interpersonal skills. The results support the conclusions that two forms of workplace learning are interrelated and, in particular, informal learning is enhanced by managers who have well-organized knowledge and skills. If managers perceive formal learning to be effective, they are more likely to utilize it and to compromise with the two different learning practices. Therefore, it might be said that the application of formal learning to work settings becomes a component of the informal learning process. From a practical standpoint, the results support the conclusions that formal learning is a reliable way to encourage managers' informal learning, and also that managers tend to synthesize their learning resulting from both formal and informal learning experiences to meet the desirable levels of work requirements, to cope with emerging problems, and to prepare for their future job and career. This study provides implications for future research and practices in workplace learning and HRD. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]