Type 1 Diabetes Mellitus (T1DM) is one of the most prevalent chronic health conditions in children under the age of 18 years. Complications of the disease include hypo- and hyperglycemia, which can have an impact on children's performance in assessment situations, in the clinic, and in school. Because there is no cure for this disease, there is a need to understand the cognitive deficits associated with some of its complications, as this knowledge will impact on the choice of treatment regimens as well as educational interventions. This paper provides a comprehensive review of the relevant literature on the neurocognitive outcome of T1DM. In particular, disease- and treatment-related variables that are associated with poor performance on cognitive domains will be reviewed. Specifically, age of onset, duration, pubertal effects, and presence of hypoglycemia or hyperglycemia will be examined. These findings are not without controversy, and limitations to conclusions will also be presented. Where relevant, recommendations for future research directions will be provided.