Self-management is integral to effective chronic disease management. Cognitive impairments (CogImp) associated with dementia have not previously been reviewed in diabetes mellitus (DM) self-care. The aims of this study are to know (1) whether CogImp associated with dementia impact self-care and (2) whether specific CogImp affects key DM self-care processes. A systematic literature search with a narrative review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. This review examined studies published from January, 2000 to February, 2016 describing the relationship between cognition and DM self-care domains in community dwelling older adults with dementia/CogImp. Eight studies met inclusion criteria. Decrements in all self-care domains were associated with CogImp. Problem solving was related to reduced disease knowledge (OR 0.87, 95% CI = 0.49-1.55), resulting in poorer glycemic control. Decision-making impairments manifested as difficulties in adjusting insulin doses, leading to more hospital admissions. People without CogImp were better able to find/utilize resources by adhering to recommended management (OR 1.03, 95% CI = 1.02-1.05). A lack of interaction with health care providers was demonstrated through reduced receipt of important routine investigation including eye examinations (ARR = 0.85, 95% CI = 0.85-0.86), HbA1c testing (ARR = 0.96, 95% CI = 0.96-0.97), and LDL-C testing (ARR = 0.91, 95% CI = 0.901-0.914). People without CogImp had better clinic attendance (OR 2.17, 95% CI = 1.30-3.70). Action taking deficits were apparent through less self-testing of blood sugar levels (20.2% vs 24.4%, P = 0.1) resulting in poorer glycemic control, self-care, and more frequent micro/macrovascular complications. Persons with diabetes and CogImp, particularly in domains of learning, memory and executive function, were significantly impaired in all self-care tasks.