Background Childhood maltreatment (CM) has been associated with suicidal ideation (SI) in children and adolescents, yet the mediating role of mindfulness in this association remains unclear. This study aims to test the mediation of mindfulness in CM-SI association among a large sample of Chinese children and adolescents. Methods A population-based cross-sectional study of 3455 children and adolescents aged 10-17 years from southwest China Yunnan province was conducted. Information from the participants was collected by using a comprehensive self-administered questionnaire. The Chinese version of the Childhood Trauma Questionnaire (CTQ), Five Facet Mindfulness Questionnaire (FFMQ), and the Beck Scale for Suicidal Ideation (BSSI) were used to measure CM, mindfulness and SI. Univariate and multivariate binary logistic regression models were used to estimate the crude and adjusted associations between CM, mindfulness and SI (one-week, one-year, lifetime). Pathway analysis was subsequently performed to test the mediation of mindfulness in CM-SI association. Results The findings showed that mindfulness, CM and SI were significantly correlated with each other (p < 0.05). Mindfulness is a significant mediator in CM-SI association, accounted for 7.5, 11.4, and 17.6% of the total associations for one-week SI, one-year SI, and lifetime SI, respectively. For the five types of CM, the highest level of mediation via mindfulness had been found for physical neglect (PN) and one-year SI (34.3%), followed by emotional neglect (EN) and one-year SI (30.2%), sexual abuse (SA) and one-year SI (25.4%). Conclusions Our study findings highlight the intervention potential of mindfulness in preventing CM associated suicidal risk. Future longitudinal studies are warranted to corroborate the effectiveness of mindfulness-based intervention for Chinese children and adolescents.