The study examined the cognitive processes involved in written sentence construction in children affected by prenatal alcohol exposure (PAE) when compared a control group of nonexposed typically developing children, and a contrast group of nonexposed children with various clinical diagnoses. Results indicated that children with PAE and those in the contrast group exhibited poorer sentence writing than the control group. Additionally, children with PAE utilized different cognitive processes to write sentences when compared to the nonexposed groups, irrespective of having a diagnosis. For children in the nonexposed groups, improved sentence writing was associated with better performance on measures of intellectual ability, verbal retrieval, verbal learning and recall, and inhibition. For children with PAE, more proficient sentence writing was associated with the same cognitive processes plus spatial working memory. This suggested that unique, altered, or inefficient cognitive functioning associated with effects of PAE impacted written sentence construction. The findings underscore the importance of considering specific cognitive processes, including spatial working memory, when assessing for writing difficulties and developing interventions for children with PAE.