Rumination and low self-esteem are associated with suicidality, and with autism spectrum disorders (ASD). However, rumination and self-esteem in relation to suicidality in adults with ASD have not been examined. This cross-sectional study (n = 75; 46 males and 29 females) investigates the relation of rumination and self-esteem to the absence/presence of suicidal ideation (SUIC+/-), history of attempted suicide (HAS), and severity of suicidality. Multivariate analysis of variance showed that self-esteem was significantly associated with SUIC+/-, whereas rumination was significantly associated with HAS. Multiple regression analysis showed that rumination and self-esteem were independently associated with severity of suicidality, but these lose their significant contribution, when statistically controlling for depression. The prevalence of suicidal ideation was 66.6%; gender was not a significant factor.