<p>In adolescents, sleep quality is closely related to physical and mental health. This study explores the influence of parent–adolescent conflict on sleep quality among Chinese adolescents while verifying the mediating role of core self-evaluation and depression and the moderating role of left-behind status. Using cluster sampling method, 4,052 adolescents were recruited from four cities in south, west, and central China. The students were assessed using self-reported scales for parent–adolescent conflict, sleep quality, core self-evaluation, and depression. After analyzing descriptive statistics and correlations, structural equation modelling was carried out in SPSS 29.0 and PROCESS 4.2. Core self-evaluation (<i>β</i> = 0.05, <i>p</i> &lt; 0.001) and depression (<i>β</i> = 0.04, <i>p</i> &lt; 0.001) had significant individual and chain (<i>β</i> = 0.03, <i>p</i> &lt; 0.001) mediating effects in the relationship between parent–adolescent conflict and sleep quality. Furthermore, the product term of parent–adolescent conflict and left-behind status had a significant predictive effect on depression (<i>β</i> = 0.11, <i>p</i> &lt; 0.001), meaning left-behind adolescents faced higher depressive risk amid parent–adolescent conflict. These findings confirm that parent–adolescent conflict impairs sleep quality by lowering core self-evaluation and exacerbating depression, with left-behind status amplifying depressive risk. Building harmonious family relationships and providing targeted support for left-behind adolescents are critical to improving their sleep quality.</p>