Suicidal thoughts and behaviors and nonsuicidal self-injury are more common in autistic adolescents than non-autistic adolescents, per parent- and self-report. Clinician-rated measures of suicide risk (e.g. Columbia Suicide Severity Rating Scale) have not been investigated with autistic youth despite high parent-child rating discrepancies. In the present study, the Columbia Suicide Severity Rating Scale was employed to assess suicidal thoughts and behaviors and nonsuicidal self-injury in 239 early adolescents (10:0-13:9 years old) without intellectual disability, of whom 138 youth were autistic. Analyses tested diagnostic- and sex-based differences in suicidal thoughts and behaviors and nonsuicidal self-injury, and youth consistency in reporting across self- and clinician-rated measures. A greater proportion of autistic youth reported lifetime suicidal ideation (33 of 138, 23.9%) and nonsuicidal self-injury (12 of 138, 8.7%) than non-autistic youth (7 of 101, 6.9% suicidal ideation; 2 of 101, 2.0% nonsuicidal self-injury); however, there were no sex-based differences. Non-autistic youth were consistent in reporting suicidal thoughts across measures, but nearly one in five autistic youth disclosed suicidal thoughts on a self-report measure, but not on the clinician-rated Columbia Suicide Severity Rating Scale. Findings suggest that autism diagnostic status, but not sex, confers significant risk for suicidal thoughts and behaviors and nonsuicidal self-injury in early adolescents and that the Columbia Suicide Severity Rating Scale may be a useful measure of suicide risk for some autistic youth, but it may not detect all autistic youth experiencing suicidal thoughts.