The writing attempts of children often feature mirror-reversals of individual letters. These reversals are thought to arise from an adaptive tendency to mirror-generalize. However, it is unclear whether mirror-writing is driven by mirror-generalisation of the visual letter forms, or of the actions for writing them. We report two studies of the relationship between mirror-writing and the ability to recognize whether a visually presented letter is in the correct orientation, amongst primary and preschool children learning to read and write in English. Children who produced more mirror-writing also made more orientation recognition errors, for uppercase (Study 1, n = 44) and lowercase letters (Study 2, n = 98), and these relationships remained significant when controlling for age. In both studies, the letters more often reversed in writing were also more prone to orientation recognition errors. Moreover, the rates of mirror-writing of different uppercase letters were closely similar between the dominant and non-dominant hands (Study 1). We also note that, in the recognition tasks, children were more likely to accept reversed letters as correct, than to reject correctly oriented letters, consistent with a tendency to mirror-generalize the visual letter forms. In every aspect, these results support a major role for visual representations in developmental mirror-writing.