Physically folding paper is a common activity performed by many children, but it is not mastered until middle-childhood. Paper folding ability has been the focus of studies motor development. There has been a long history in cognitive science of assessing spatial skills through mental paper folding tests. Despite the similarities between physical and mental paper folding, it is currently unknown whether there is a relation between physically and mentally folding paper. This study examined 107, 3- to 8-year-old children in both skills. Our results show that children of all ages were able to physically fold paper, but became more accurate with age. Additionally, we found that there is a significant relation between physical and mental paper folding, and that this relation was robust to different statistical controls and statistical specifications. We discuss how these results influence our understanding of the co-development of cognitive and motor skills.