Purpose <p>Attenuated positive symptoms constitute the most validated vulnerability marker for psychosis in non-autistic young adults. Early deviations in executive functioning and social cognition are believed to contribute to the onset of these symptoms. This study evaluates the presence of psychotic symptoms in autistic young adults and their putative cognitive precursors.</p> Methods <p>Thirty young adults diagnosed with an autism spectrum condition (ASC; M_age=20.1; 83.3% male) were assessed for psychotic symptoms. Their scores were compared to a typical peer comparison group (TC; M_age=22.1, 41.7% male) and, retrospectively, to their scores in childhood (M_age=12.1) to determine long term-stability. In addition, it was tested whether cognitive markers assessed in childhood could predict positive symptoms in young adulthood.</p> Results <p>There was significant and moderate evidence for more negative symptoms in young adults with ASC compared to TC, but no difference in positive or disorganized symptoms. Furthermore, positive and negative symptoms did not differ significantly over time and displayed weak correlations between both assessments, while disorganized symptoms showed a modest decrease and a significant correlation. In addition, response inhibition accuracy in childhood was a significant cognitive predictor of positive symptoms at follow-up.</p> Conclusions <p>Contrary to expectations, our results suggest that self-reported positive psychotic symptoms are not elevated in young adults with ASC. Psychotic symptoms remain relatively stable from childhood to young adulthood, although individual differences in symptom change are substantial. Response inhibition is a putative candidate risk marker for the development of positive symptoms in young, autistic adults that awaits further replication in large samples.</p>