Duration estimation is a conceptual ability that plays a crucial role in human behavior. Impairments in duration estimation ability have a significant impact on daily autonomy and social and cognitive capacities, even more so in psychological disorders. It has been recently shown that the ability to estimate durations develops at a slower pace in individuals with mild intellectual disability (MID) compared to typically developing (TD) individuals. More generally, it has been also demonstrated that duration estimation requires working memory updating. In the present study, we compared the duration estimation and updating performances of individuals with idiopathic MID without associated disorders aged from 10 to 20 years to those of typical individuals of the same ages (N = 160). Our results highlight a developmental lag not only in the capacity to estimate short durations (< 1 second) in individuals with idiopathic MID, both in a bisection task and in a reproduction task, but also in working memory updating capacity. The findings also emphasize - for the first time - the importance of updating for both the age-related increase in duration estimation capacities and the deficits of these capacities in idiopathic MID. This is consistent with the hypothesis that duration estimation deficits in idiopathic MID may be due, to a large extent, to lower updating abilities.