This study aims to examine several things. First, it examines the appropriateness of designating in-company trainers for a work-learning dual system. Next, it examines the moderated-mediating effect of learning transfer climate (LTC) on the in-company trainer's on-the-job training, and the correspondent work-learner's learning transfer (LT). Subjects were small and medium-sized Korean businesses in mechanical and robotics industries, electrical and electronic industries, and information technology sectors. Trainers were asked about the appropriateness of their selection criteria, including consideration for various competencies and aspects of on-the-job training. Learners were asked about LT and LTC. A total of 349 data set points were collected from the trainers and learners and used for data analysis. Analyses found several things. First, appropriate trainer selection criteria, on-the job training performance levels, learner's LT and LTC are positively correlated. Second, a trainer's OJT performance fully mediates trainer selection criteria and the corresponding learner's LT. Third, the moderated mediating effect of LTC was not statistically significant. Implications of the study and directions for future research propose points to improve the effectiveness of work-learning dual system OJT.