We tested a novel framework for explaining individual differences in academic performance with a large sample of undergraduates (n = 263). Using structural equation modeling, we evaluated how cognitive abilities, disposition, and healthy lifestyle separately influence grade point average. Employing a large cognitive battery assessing eight cognitive constructs and a bifactor model, we parsed variance due to general cognitive ability and residual specific cognitive abilities. Participants wore a Fitbit watch for three weeks to track activity levels, and completed the Big Five Inventory. We found that general cognitive ability did not predict academic performance after accounting for specific abilities, conscientiousness, and physical activity, but the specific abilities secondary memory and fluid intelligence each uniquely predicted about 4% of the variance in grade point average. Neither conscientiousness nor physical activity contributed unique variance in academic performance after accounting for other factors.