Objective: There is increasing recognition that socio-cognitive skills, such as moral reasoning (MR), are affected in a wide range of developmental and neuropsychological conditions. However, the lack of appropriate measures available to neuropsychologists poses a challenge for the direct assessment of these skills. This study sought to explore age-related changes in MR using an innovative visual tool and examine the developmental sensitivity of the task. Method: To address some of the methodological limitations of traditional measures of MR, a novel, visual task, the Socio-Moral Reasoning Aptitude Level (So-Moral), was used to evaluate MR in 216 healthy participants aged 6-20years. Results: The findings show a linear increase in MR from childhood to late adolescence with significant group differences between childhood (6-8years) and preadolescence (9-11years), and between early adolescence (12-14years) and middle adolescence (15-17years). Conclusions: Interpreted in light of current brain development research, the results highlight age-related changes in MR that offer insight into typical MR development and opportunities for comparisons with clinical populations. The findings also provide evidence of the potential of the So-Moral as a developmentally appropriate measure of MR throughout childhood and adolescence.