Autism spectrum disorder (ASD) characteristics seem to abate over time, but whether this protracts until late adulthood is largely unknown. We cross-sectionally investigated self- and other-reported ASD characteristics of adults with (ASD: Nmax-self = 237, Nmax-other = 130) and without ASD (COM: Nmax-self = 198, Nmax-other = 148) aged 19–79 years. Within the ASD group, self-reported ASD characteristics, and sensory sensitivities were highest in middle adulthood, while age was not associated to empathy. Sex differences were also found. However, age-and sex-related differences were not revealed by others and self- and other-report were poorly concordant. These results show that ASD characteristics in adulthood are differently perceived across age, sex, and informants and suggest that it is important to repeatedly assess self-reported ASD characteristics during adulthood.