Introduction <p>The increasing use of short video platforms among adolescents has raised concerns about problematic usage, which can lead to detrimental outcomes. This study investigates the bidirectional associations between mindfulness, negative cognitive processing bias, and problematic short video use (PSVU) in adolescents, considering mindfulness as a potential protective factor.</p> Methods <p>The study utilized longitudinal data from two time points, separated by a 6-month interval. A total of 364 adolescents (177 boys; <i>M</i>_age = 14.23, <i>SD</i> = 1.05) from public middle schools in Hubei Province, China, participated in this study. Cross-lagged panel models and mediation analyses were used to examine the relationships among mindfulness, negative cognitive processing bias and PSVU.</p> Results <p>The results showed that mindfulness at T1 significantly predicted lower PSVU at T2, whereas PSVU at T1 did not predict mindfulness at T2. Mindfulness at T1 negatively predicted negative cognitive processing bias at T2, and negative cognitive processing bias at T1 negatively predicted mindfulness at T2. Negative cognitive processing bias at T1 significantly predicted higher PSVU at T2, and PSVU at T1 also predicted increased negative cognitive bias at T2. The study also found that mindfulness at T1 indirectly predicted PSVU at T2 via NCPB in a half-longitudinal mediation model, such that T1 mindfulness predicted T2 NCPB and T1 NCPB predicted T2 PSVU.</p> Conclusions <p>Mindfulness serves as a protective factor against PSVU by reducing negative cognitive biases, which in turn mitigates problematic short video use. The study highlights the importance of supporting the development of adolescents’ dispositional mindfulness to counteract the adverse effects of short video platforms. Future interventions targeting mindfulness and cognitive bias could be pivotal in reducing PSVU among adolescents.</p>