Purpose: The purpose of this study is to identify the causal relationship among informal learning, leader-member exchange (LMX), empowerment, job characteristics and job self-efficacy and the impact on administrative assistants in corporations. The study aims at providing information for administrative assistants who have worked with their current supervisors for more than one year in a one-to-one administrative assistant role in corporations. Design/Methodology/Approach: To ensure the reliability and validity of the questions, statistical analysis was performed using SPSS 18.0. AMOS 18.0 was also used to estimate the causal relationship of the proposed research model. Findings: The analyses show the following results. Indirect factor loading of LMX and empowerment to informal learning and direct factor loading of job characteristics and job self-efficacy were observed. In the relationship between LMX and informal learning, empowerment had a negative mediating effect and job self-efficacy had a positive mediating effect. In the relationship between empowerment and informal learning, job self-efficacy and job characteristics both had a mediating effect. However, job self-efficacy did not have a mediating effect in the relationship between job characteristics and informal learning. Originality/Value: When considering informal learning, planners should consider both individual characteristics and organizational characteristics. However, informal learning is not directly correlated to the impact of factors related to the executives and organization itself, but rather linked to individual and job characteristics. Hence, promoting job self-efficacy not only requires the individual efforts of employees but also a systematic strategy at the corporate level.