An individual’s cognitive ability is arguably the single most important construct in work performance. The general factor of intelligence, g, is widely considered “as good as it gets” when attempting to predict work performance. However, development and continued understanding of the g factor of intelligence is lacking within the field of I-O psychology. This thesis aims to investigate the mediation of the intelligence-performance relationship by cognitive factors, most importantly, Executive Function. While the hypotheses of this study were not supported, this research serves to provide a framework for investigating intelligence within I-O as well as explore the relationship between Executive Function, various cognitive factors, and general intelligence in the performance domain.