The purpose of this study was to determine whether the cognitive abilities of listening and reading comprehension and morphological awareness affect children’s writing to dictation. Data were collected from 194 first-grade elementary schoolchildren in South Korea on the effects of repetitive practice and memorization by comparing impromptu and one semester’s regular dictation tests. The results first revealed that spelling, spacing, and punctuation were highly correlated with the three cognitive abilities in the impromptu writing to dictation, but far less in the regular dictation test. Second, it was found that children’s listening and reading comprehension and morphological awareness influenced their spelling, while reading comprehension and morphological awareness affected spacing and punctuation significantly in the impromptu dictation test. However, in the case of the regular dictation test, which involved memorization, the number of significant factors was small, and final explanatory power of those cognitive abilities was much smaller.