The relationship between callous-unemotional (CU) traits (the affective facet of psychopathy and the psychopathy that occurs during childhood and adolescence) and suicide ideation (SI) remains unclear. The mechanisms underlying this association still have a gap in the literature. The aims of this study were to determine whether and how callous-unemotional traits were associated with suicide ideation, and to evaluate the mediating effect of negative affect (includes irritability, depression, and anxiety) and the moderating effect of future orientation on the association.Data were extracted from a longitudinal study involving middle and high school students, with 1,913 students (55.3% girls) aged 11 to 19 years (14.9 ± 1.6 years) completing a self-reported online survey. The conditional process analysis was examined using Mplus 8.3.We found that callous-unemotional traits positively predicted youths' current suicide ideation, with the observed positive relationship partly mediated by negative affect. However, callous-unemotional traits did not predict the worst-point suicide ideation, which indicated the connection fully mediated by negative affect. Furthermore, future orientation moderated these indirect effects.Use of self-report measures and cross-sectional design.These findings provided evidence for current debates and conflicting conclusions, and set the foundation for future research, as well as implied the important intervention goals for reducing suicide ideation in youth.