This study tests a process model of learning in which trainer and trainee traits are simultaneously considered as endogenous variables of learning outcomes. The article builds on a social view of training and similarity-attraction paradigms. In this context, the authors hypothesize that trainer-trainee similarity in personality (agreeableness) engenders social reactions that influence how much trainees learn. To test the study hypotheses, undergraduate students (N = 194) participated in a training program during an academic semester. Results from structural-equation modeling indicate that similarity in personality acted on trainees' emotional states, which, in turn, accounted for trainees' posttraining declarative knowledge. With the use of hierarchical regression procedures, results indicated that personality similarity explained incremental variance of posttraining declarative knowledge beyond modal learning correlates (e.g., cognitive abilities, conscientiousness). The results provide evidence of a social view of training in which combined attributes of dyads (trainer-trainee) account for learning results that the extant literature primarily relates to individual-level variables (e.g., cognitive abilities). The discussion section addresses theoretical implications of the findings, with special emphasis on compositional approaches of personality. From an applied perspective, the authors discuss why corporate trainers should consider the role of their personality in training, and they also make suggestions for weighting the effect of personality similarity when evaluating training results. In this study, the authors center their attention on the trainer-trainee (T-T) dyad. Specifically, they explore how social reactions emerging from T-T's contacts impact trainees' learning processes. The notion that training is a social event suggests that interpersonal reactions (e.g., affiliation, rejection) may be operating in training. However, little is known about how trainees socially respond to trainers and, ultimately, how these responses may influence learning. The authors rely on similarity-attraction theory to hypothesize social reactions in training. Because individuals prefer to relate socially with those they perceive as similar, T-T's similarity (or lack thereof) can modify trainees' states in training, potentially altering learning outcomes. This article describes a process model that depicts the hypothetical paths connecting T-T's similarity to learning outcomes. The authors review interpersonal attraction theory with the goal of laying the theoretical foundations for the hypothesized model. (Contains 1 figure and 2 tables.)