Background <p>Sleep disturbance is highly prevalent among college students and poses significant risks to mental health. However, the longitudinal relationships among parent–child alienation, peer alienation, and sleep disturbance remain poorly understood, particularly regarding gender differences.</p> Methods <p>A three-wave longitudinal study involving 4,852 Chinese college students was conducted. The Random Intercept Cross-Lagged Panel Model (RI-CLPM) was used to examine bidirectional associations and mediating effects, and multigroup analyses were conducted to assess gender differences.</p> Results <p>At the within-person level, parent–child alienation and sleep disturbance reciprocally predicted each other (<i>β</i> = 0.112–0.121 and <i>β</i> = 0.060–0.066, respectively; <i>p</i> &lt; .05). Peer alienation predicted subsequent sleep disturbance in the total sample (<i>β</i> = 0.064–0.066, <i>p</i> &lt; .01), but this association was significant only among girls (<i>β</i> = 0.222–0.274, <i>p</i> &lt; .001). Sleep disturbance, in turn, predicted subsequent peer alienation in both genders. Furthermore, peer alienation mediated the association between parent–child alienation and sleep disturbance in the total sample (indirect effect = 0.006, 95% CI [0.002, 0.013]). Gender-specific analyses revealed partial mediation in both directions among girls (indirect effects = 0.047, 95% CI [0.026, 0.068] and 0.012, 95% CI [0.002, 0.023]), whereas no significant mediating effects were observed among boys. The standardized within-person effects were generally small (most <i>β</i>s &lt; 0.12), suggesting a multifactorial etiology.</p> Conclusion <p>Peer alienation partially mediated the longitudinal association between parent–child alienation and sleep disturbance among girls but not among boys. These findings highlight interpersonal alienation as a meaningful target for gender-sensitive prevention and early-identification efforts aimed at improving sleep health among college students.</p>