<p>Psychological factors like unhealthy personality traits, trouble managing emotions and behaviors, and poor sleep habits may contribute to insomnia. But we don’t yet fully understand how these factors interact in a chain of effects that changes how severe insomnia is. This study aimed to look at how maladaptive personality traits, self-regulation, and sleep hygiene relate to insomnia severity, using a step-by-step serial mediation model. This cross-sectional study was conducted among a college student sample in Iran. A total of 483 individuals were analyzed, of whom 349 (72.3%) were female, with a mean age of 22.7 ± 5.2 years. Data were collected using several standardized self-report questionnaires. Pearson correlation coefficients and mediation analysis were employed for data analysis. Maladaptive trait domains of personality directly negatively affected self-regulation and sleep hygiene, and lower self-regulation was also associated with poorer sleep hygiene. Both poor sleep hygiene and maladaptive domains of personality directly increased insomnia severity, whereas higher self-regulation was associated with reduced insomnia severity. Additionally, self-regulation and sleep hygiene acted as mediating variables in the relationship between maladaptive personality traits and insomnia. It can be concluded that self-regulation and sleep hygiene play mediating roles in the relationship between maladaptive personality traits and insomnia. Specifically, maladaptive personality traits, when combined with low self-regulation, lead to poorer sleep hygiene and ultimately increase insomnia severity. Therefore, it is recommended that therapists focus on strengthening self-regulation skills in individuals suffering from insomnia.</p>