This study examined the relations among loneliness, friendship, and emotional functioning in adults (N = 108) with autism spectrum disorders. Participants completed self-report measures of symptoms of autism spectrum disorders, loneliness, number and nature of friendships, depression, anxiety, life satisfaction, and self-esteem. The results indicated that loneliness was associated with increased depression and anxiety and decreased life satisfaction and self-esteem, even after controlling for symptoms of autism spectrum disorders. In addition, greater quantity and quality of friendships were associated with decreased loneliness among adults with autism spectrum disorders. Multivariate models indicated that friendship did not moderate the relationship between loneliness and well-being; however, number of friends provided unique independent effects in predicting self-esteem, depression, and anxiety above and beyond the effects of loneliness. This was the first study to examine the relations among these aspects of social and emotional functioning in adults with autism spectrum disorders, and the results indicate that this topic warrants further clinical and research attention.