Background The objective of this study was to investigate the contributions of mental health status and attitudes towards suicide on suicidal ideation in a sample of 6568 Chinese children and adolescents in China. Attitudes towards suicide were investigated as a possible moderator and mediator of the influence of mental health status on suicidal ideation. Methods Descriptive statistical analyses, Pearson correlation analyses and hierarchical regression analyses were adopted as methods of data analyses. Results Approximately 35.38% of children and adolescents in our study reported having suicidal ideation. Mental health status and attitudes towards suicide both had an independent effect on the severity of suicidal ideation. Results indicated that mental health status was positively associated with suicidal ideation, while attitudes towards suicide were negatively associated with suicidal ideation. Moderation analysis showed that the impact of mental health status on suicidal ideation was significantly greater among children and adolescents who reported favourable attitudes towards suicide. Attitudes towards suicide partially mediated the link between mental health status and the severity of suicidal ideation. Specifically, students who experienced poorer mental health status might be more likely to report significantly more favourable attitudes towards suicide, which in turn promote greater suicidal ideation. Conclusions These results have implications for the prevention of youth suicide, suggesting that mental health status and attitudes towards suicide could be important targets for prevention and intervention for children and adolescents at risk of suicidal ideation.