<p>Sleep procrastination is prevalent among college students, yet existing studies rarely examine its underlying biopsycho-behavioral mechanisms from an integrative perspective. Longitudinal evidence on how biological, psychological, and behavioral factors jointly contribute to sleep procrastination remains limited. To address this gap, this study applied the Interaction of Person-Affect-Cognition-Execution (I-PACE) model to explore the biopsycho-behavioral pathways to sleep procrastination among Chinese college students. The study contributes to the field by providing the first empirical test of the I-PACE model in the context of sleep procrastination and by identifying key mediating processes and core risk nodes using both structural equation modeling and network analysis. A longitudinal design with two time points (T1 and T2, seven months apart) was adopted. A convenience sample of 1,423 undergraduates completed the Sleep Procrastination Scale, the Mobile Phone Addiction Index, Dysfunctional Beliefs and Attitudes about Sleep Scales, the Fear of Missing Out Index, and the Morningness-Eveningness Questionnaire. Structural equation modeling and item-level network analysis were used to test the proposed hypotheses. Sleep procrastination, problematic mobile phone use, sleep emotion, sleep cognitive function, and fear of missing out (FoMO) were significantly positively correlated at T1 and T2 time points. T1 sleep biological rhythms were negatively correlated with T1 sleep emotion, T1 FoMO, T1 problematic mobile phone use, and T2 sleep procrastination. A chain mediating effect was identified: T1 sleep emotion, sleep cognition, and problematic mobile phone use sequentially mediated the relationship between T1 sleep biological rhythms and T2 sleep procrastination. Network analysis revealed that MPAI10 (a measure of mobile phone addiction) was the core node with the highest expected influence. Although FoMO was not significant in the longitudinal pathway, it showed high predictive power within the network, suggesting its role as an activated risk factor. The I-PACE model effectively elucidates the biopsycho-behavioral mechanism of sleep procrastination. Sleep biological rhythms generate maladaptive sleep-related cognitions and emotions, which negatively reinforce problematic mobile phone use and ultimately perpetuate sleep procrastination. These findings advance theoretical understanding of sleep procrastination and offer potential targets for intervention.</p>