Background <p>Rumination is regarded as a cognitive risk factor and a focal point of clinical interventions aimed at mitigating suicidal ideation. Nonetheless, the mechanisms how rumination affects suicidal ideation warrant further exploration.</p> Methods <p>A cohort of 831 Chinese college students (<i>M</i> age = 19.30 years, <i>SD</i> age = 1.17; 444 females) completed a questionnaire composed of the Ruminative Responses Scale, Entrapment Scale, Mindfulness Attention Awareness Scale, and Self-Rating Idea of Suicide Scale. A moderated mediation model was used to explore the relationship between rumination, entrapment and suicidal ideation.</p> Results <p>The results reveal that: (1) Rumination significantly and positively predicts suicidal ideation among college students (<i>β</i> = 0.26, <i>p</i> &lt; 0.001); (2) Entrapment serves as a mediating role between rumination and suicidal ideation (95% CI= [0.27, 0.42]); and (3) Mindfulness moderates the impact of rumination on suicidal ideation (<i>β</i> = -0.09, <i>t</i> = -4.30, <i>p</i> &lt; 0.001).</p> Conclusions <p>These findings highlight entrapment as the mediator linking rumination to suicidal ideation and emphasize the potential advantages of enhancing mindfulness to alleviate suicidal ideation among Chinese college students, bearing significant implications for the prevention and intervention of suicidal ideation in this demographic.</p> Clinical trial number <p>Not applicable</p>