Objective This study examined autism spectrum disorder (ASD) features in relation to treatment completion and eating disorder psychopathology in anorexia nervosa (AN). Method Thirty‐two adult women were recruited from specialist eating disorder services. Features of ASD and disordered eating were measured. Premature termination of treatment was recorded to explore whether ASD traits had impact on early discharge. A healthy control group was also recruited to investigate ASD traits between clinical and nonclinical samples. Results Significant differences were found between the AN group and the healthy control group in obsessive‐compulsive disorder traits, depression and anxiety and ASD traits, with significant differences between groups in Social Skill and Attention Switching. The AN group reported no significant relationship between disordered eating severity and ASD traits. No significant effect was found between ASD features and treatment completion. Discussion Raw data on premature termination of treatment, despite no statistic impact, showed that seven out of the eight participants with high features of ASD completed treatment as planned compared with 50% of those with low ASD traits. Unexpectedly, this suggests enhanced treatment adherence in ASD. Copyright © 2013 John Wiley & Sons, Ltd and Eating Disorders Association.