Objectives: Bedtime procrastination (BP) is defined as the behavior of voluntarily postponing bedtime without having external reasons for doing so. According to previous studies, people with reduced use of active emotion regulation strategies may use BP to cope with negative emotions. However, research about the relationship among active emotional regulation strategies, BP, and insomnia is lacking. This study aimed to investigate the mediating effect of BP between active emotional regulation strategies and insomnia severity. Methods: In total, 597 adults (female, 81.9%; mean age, 23.18±2.80 years) completed the Emotional Regulation Strategies Checklist, Insomnia Severity Index, and Bedtime Procrastination Scale. Results: There was a significant association between active emotional regulation strategies and BP (r=-0.152, p<0.01), between BP and insomnia severity (r=0.259, p<0.01), and between active emotional regulation strategies and insomnia severity (r=-0.128, p<0.01). BP significantly mediated the relationship between active emotional regulation strategies and insomnia severity (B=-0.024; 95% confidence interval [CI], -0.04 to -0.01). Conclusions BP may be considered in the relationship between active emotional regulation strategies and insomnia severity. Understanding the mediating role of BP may help prevent insomnia.