The assessment of preschoolers with prenatal alcohol exposure (PAE) is challenging for many diagnostic teams and clinicians. The 2016 Canadian Fetal Alcohol Spectrum Disorder (FASD) diagnostic guidelines describe the assessments recommended for individuals with PAE in various age groups. Interpretation of brain domains constituting global impairment in preschoolers is not well described in the literature, and there has been clinical reluctance to consider the interpretation of clinical assessments as definitively diagnostic in this age group. This study describes the results of 10-year retrospective clinical data of over 300 preschoolers with PAE referred to the Manitoba FASD Centre for assessment of FASD. Preschoolers who met the criteria for a diagnosis of FASD showed significantly greater global developmental impairment, compared with those with PAE alone. They also demonstrated poorer receptive and expressive language abilities when compared with preschoolers who were not diagnosed. Preschoolers with FASD were rated as having more difficulties with executive functioning skills and adaptive functioning skills, compared to their counterparts. Significant deficits were found in fine-motor, visual-motor, and components of gross-motor skills. Importantly, significant sensory processing differences are particularly evident in preschoolers and are important in understanding behavior and in intervention planning. Together, standardized assessment of motor and sensory processing skills, with a comprehensive assessment of language, are significant predictors of FASD diagnosis for preschoolers with PAE.