The present study aimed to investigate the mediating roles of difficulties in emotion regulation and self-esteem in the relationship between insecure attachment styles and nomophobia. The research method was descriptive–correlational based on structural equation modeling (SEM). The statistical population consisted of upper-secondary school students in Kermanshah, from whom 480 students were selected using cluster random sampling. Participants completed the Nomophobia Questionnaire (Yildirim & Correia), the Attachment Styles Scale (Collins & Read), the Difficulties in Emotion Regulation Scale (Bjureberg et al.), and the Rosenberg Self-Esteem Scale. Data were analyzed using SPSS and AMOS software. The findings indicated that anxious attachment style was significantly related to nomophobia both directly and indirectly, through the mediation of difficulties in emotion regulation and self-esteem (p < .05). In contrast, avoidant attachment style did not have a significant direct effect on nomophobia, but its indirect effect through the mediation of difficulties in emotion regulation and self-esteem was significant. Fit indices also indicated that the empirical model had an acceptable fit. Moreover, the coefficient of determination of the model showed that the predictor variables could explain 53% of the variance in nomophobia. Based on the findings of this study, it is recommended that preventive and educational interventions be designed and implemented with the aim of managing smartphone use and identifying the predisposing factors of nomophobia, including insecure attachment styles. These interventions can focus on strengthening emotion regulation skills and promoting adaptive patterns of smartphone use, with the goal of reducing nomophobia and preventing its associated psychological consequences.