AbstractAimTo describe the development of cognitive empathy across the lifespan from a very large cohort using a standardized measure of cognitive empathy ability.MethodParticipants (n=4545, age bands <5y to >75y, 60% female) were a convenience sample recruited voluntarily from visitors to the Glasgow Science Centre in the UK, who completed the Reading the Mind in the Eyes Test.ResultsWhen compared to preceding age groups, we found significant developmental gains in empathy ability in children aged 6 to 7 years (p=0.048, d=0.45) and again at 10 to 12 years (p=0.042, d=0.23), followed by a slight reduction in ability during adolescence (p=0.087, d=–0.18), and functional maturity in those aged 19 to 25 years (p=0.001, d=0.76). Cognitive empathy abilities remained relatively stable across adulthood but gradually declined in people over 65 years, with notable decline in males over 75 years (p=0.001, d=–0.98). Females performed better than males at all ages.InterpretationUnderstanding developmental issues in cognitive empathy could influence approaches to moral and social education for children, and health and social care support for older people. Standardized cognitive empathy tests could also provide novel approaches in the early detection of developmental vulnerabilities in a range of neurological conditions, and within neuropsychiatric and neurodegenerative disorders in which cognitive empathy is known to be impaired.What this paper adds Cognitive empathy is a late‐developing ability and changes across the lifespan. Cognitive empathy increases during childhood but with potentially altered abilities during adolescence. Cognitive empathy matures during early adulthood and gradually declines in older age. There is a female advantage in cognitive empathy abilities.