Background: The purpose of the current study was to examine how the morphological structure of a real word or novel word affected the incidental vocabulary learning of participants and to examine how these target items are processed as they are read. In addition, we examined the roles of vocabulary depth and breadth in the process of incidental vocabulary learning. Methods: We had participants read short passages that contained real words or novel words that differed on their morphological accessibility as we collected eye movement data. Participants also completed several vocabulary depth and breadth measures. Results: Accessible real words and novel words were learned better than inaccessible and less accessible items, but there was a processing cost associated with accessible real words compared with inaccessible real words. In contrast, participants spent more time on the less accessible novel words compared with accessible novel words, but that extra processing time did not translate into better acquisition scores. Finally, both vocabulary breadth and depth explained variance in incidental vocabulary acquisition, while breadth explained variance in gaze duration and depth explained variance in regressive eye movements. Conclusions: Accessibility of the targets affected both acquisition and reading time, and depth and breadth are both individual differences that explain variance in incidental acquisition and the processing of those words.