Impulsivity, cognitive arousal, and sleep quality are critical factors affecting college students' well-being and academic performance. While impulsivity negatively influences sleep quality, the mediating role of cognitive arousal remains underexplored. The present study assesses how impulsivity affects sleep quality through cognitive arousal. Specifically, it explores whether impulsive behavior heightens cognitive arousal, leading to impaired sleep quality, and whether these relationships hold over time. A longitudinal design was employed, collecting data from 521 college students across three waves over an academic year. Standardized questionnaires were administered to measure impulsivity, cognitive arousal, and sleep quality at each wave. Structural equation modeling and random-intercept cross-lagged panel models (RI-CLPMs) were utilized to analyze the associations, assessing both the direct effects and the mediating role of cognitive arousal over time. Impulsivity significantly predicted increased cognitive arousal over time, which in turn negatively affected sleep quality. Cognitive arousal was confirmed as a significant mediator in the relationship between impulsivity and sleep quality. These relationships remained consistent across the three-time points, with significant direct effects of impulsivity on cognitive arousal and cognitive arousal on sleep quality. Interventions to reduce cognitive arousal and impulsivity-related behaviors could improve sleep quality among college students. Future research should explore additional environmental and psychological factors influencing these relationships.