The relationships between knowledge and regulation of cognition and how they interact to mediate the effects of task-induced involvement load on word learning and confidence judgments were investigated. The participants were 77 undergraduate English majors. They were required to complete a checklist on metacognition. Subsequently, they were assigned to complete three tasks with varying degree of involvement load. They were then required to rate their confidence in learning and using the target words. Pre- and post-study vocabulary tests were administered to measure improvement in word learning. According to the checklist on metacognition, the learners were assigned to four different ability groups. The results showed that knowledge of cognition is a good predictor of the confidence judgments, in the same way that regulation of cognition is a good predictor of the confidence judgments. In terms of learners' actual word learning performance, task-induced involvement load is mediated significantly by the regulatory competence but not by the knowledge of cognition. There is a discrepancy between learners' self-assessment and actual performance. Relevant educational implications are discussed.