<p>Nonsuicidal self-injury (NSSI) and suicidal ideation are serious mental health problems among emerging adults. However, few studies considered NSSI and suicidal ideation together and distinguished the functions of abuse/neglect. This study utilized a two-wave longitudinal design to investigate the sex-specific effects of child abuse/neglect on NSSI/suicidal ideation and to assess the mediating roles of expressive suppression and cognitive reappraisal. A total of 848 Chinese college students with child maltreatment experiences (53.2% females; <i>M</i>_age = 19.08, <i>SD</i> = 1.43) were included. Child abuse/neglect and expressive suppression/cognitive reappraisal were assessed at Time 1, and NSSI and suicidal ideation were assessed at Time 2. The mediating effects were examined using structural equation modeling with bias-corrected bootstrapping. Meanwhile, model comparison was conducted for sex differences. The results suggested that child abuse positively predicted suicidal ideation for females, while child neglect positively predicted suicidal ideation for males. Moreover, child abuse positively predicted NSSI through expressive suppression for females. Also, child neglect positively predicted NSSI and suicidal ideation by reducing cognitive reappraisal for both males and females. Our research underscores the culturally distinct sex-differentiated impacts of abuse versus neglect on NSSI and suicidal ideation within the Chinese cultural context. Furthermore, these findings emphasize the critical importance of developing adaptive cognitive emotion regulation strategies that account for sex-specific maltreatment histories to prevent NSSI and suicidal ideation among emerging adults.</p>