Previous research has documented that cognitive conflict affects basic cognitive processes such as memory, reasoning, and attention allocation. However, little research has explored whether its effect can be extended to higher cognitive processes such as metacognitive monitoring. The current study took a novel variant of a Stroop task that employed words presented in a color opposite to the color of the object itself (e.g., heart, presented in green) or same as the color of the object (e.g., forest, presented in green) as targets, an important form of metacognitive monitoring-judgments of learning (JOLs) was used as the measurement index to investigate the influence of cognitive conflict on metacognitive monitoring and to delineate the potential mechanisms underlying the cognitive conflict effect on JOLs. In Experiment 1, results showed that participants gave higher JOLs to consistent than to conflict words, even though cognitive conflict had little influence on memory recall. Experiment 2, employing a selfpaced study task, found that conflict words were processed less rapidly than consistent ones, and the difference in processing fluency significantly mediated the cognitive conflict effect on JOLs. Experiment 3 employed an observer-learner task; the mediation analysis showed a complete mediation role of metamemory beliefs (observation JOLs) in the relationship between word type and JOLs. In Experiment 4, research results suggested that participants' beliefs about processing fluency played an important role in the cognitive conflict effect. To conclude, cognitive conflict is a reliable factor affecting higher cognitive processes (metamemory monitoring). Both processing fluency and metamemory beliefs tend to contribute to the cognitive conflict effect.