Until now, a successful application of the mental rotation paradigm was restricted to children 5?years or older. By contrast, recent findings suggest that even infants can perform mental rotation. Unlike the methods used in infant studies (looking time), our new research paradigm allows for the measurement and interpretation of reaction times. Kindergartners (aged 3-6?years) were presented with a stimulus configuration on a touchscreen and asked to bring a rotated stimulus into an upright position using the shortest path. Mean reaction time (RT) increased linearly with angular disparity. The ensuing linear trend was significant not only for the entire sample but also for the youngest age group analysed separately. To exclude the possibility that linearity was due to movement planning, 3-year-olds had to manually rotate a stimulus about the same trajectory without the need for a corresponding mental transformation in a second experiment. Here, no linear trend was observed. These results are interpreted as evidence for an analogue mental transformation in 3-year-olds, equal to the transformation processes in older children's and adults' mental rotation.