Understanding the processes through which trainee characteristics influence learning is important for identifying mechanisms that drive training effectiveness. We examine the direct and indirect paths through which core self-evaluations (CSE) impact learning. We also include general cognitive ability (GCA) to explore whether CSE’s paths to effectiveness differ from those of a well-documented predictor of learning. We proposed a model in which CSE contributes to training effectiveness through its influence on motivational intervening mechanisms, and we tested this model empirically with military personnel (N = 638) who participated in job-required training. The data supported a partially mediated model. Irrespective of inclusion of GCA as a control variable, motivation and effort allocation (MEA) process variables (i.e., training motivation, midtraining self-efficacy, and midtraining goal setting) mediated (or partially mediated) the relationship between CSE and training outcomes that included affective (e.g., intentions to transfer), cognitive (e.g., declarative knowledge), and skill-based (e.g., proficiency) learning. Conversely, GCA had neither direct nor indirect effects on affective learning but did demonstrate direct effects on cognitive and skill-based learning. Results support the utility of including CSE in training research and practice, suggest that MEA serves as an explanatory mechanism for CSE’s relation to learning outcomes, and demonstrate that CSE and GCA differentially influence training effectiveness and do so through different explanatory mechanisms.