Background and Objective: Research indicates that loneliness and emotional and behavioral problems increase the risk of suicidal ideation in adolescents, but less is known about the distinct contributions of these problems. We aimed to distinguish the pathways through which loneliness, internalizing problems and externalizing problems contribute to suicidal ideation in Chinese adolescents. Methods: We did a longitudinal mediation analysis with data collected at three time points (2021.05, 2021.10, 2022.05) from 27 Taizhou high schools. Loneliness and suicidal ideation were assessed using the UCLA 3-Item Loneliness Scale and one suicide item from the Children's Depression Inventory, respectively. The Strength and Difficulties Questionnaire assessed internalizing (emotional and peer problems) and externalizing problems (conduct and hyperactivity problems). Structural equation modelling was used to construct complete longitudinal path models. Results: Using data from 2254 adolescents of junior and senior high schools, we identified bi-directional associations between any two variables of loneliness, internalizing/externalizing problems and suicidal ideation. Most notably, loneliness predicted worse subsequent internalizing problems (β=0.376, p<0.001) and externalizing problems (β=0.291, p<0.001), which in turn predicted more severe suicidal ideation (β=0.024, p<0.001; β=0.020, p<0.001). Effect sizes of the longitudinal mediations were 39% and 21% respectively. The reverse pathways were statistically supported as well, suggesting bi-directional influences. Conclusions: Loneliness, internalizing problems and externalizing problems were strongly intertwined with suicidal ideation in adolescents. Public health initiatives could reduce loneliness and emotional and behavioral problems by implementing multifaceted interventions, thereby breaking the vicious circle and protecting against the development of suicidal ideation.