Endothelial cells (EC) and vascular smooth muscle cells (VSMC) are involved in the development of local and diffuse vasculopathies by participating in inflammatory processes that can lead to uncontrolled vascular complications. Our aim was to study the possible interactions of EC and VSMC in an in vitro coculture model exposed to diabetic-like conditions and the effect of vitamin D on cellular pathways that might lead to an inflammatory response. EC and VSMC were isolated from different umbilical cords and stimulated in an in vitro coculture model in a diabetic-like environment and calcitriol for 24 h. Total RNA and protein were extracted from cells and analyzed for the expression of selected inflammatory-related markers. The EC-VSMC coculture in a diabetic-like environment induced the expression of inflammatory markers such as Kruppel-like factors, thioredoxin-interacting protein (TXNIP), IL-6, and IL-8. Addition of vitamin D to the EC-VSMC coculture induced selective changes in the inflammatory response. This model could lead to a better understanding of the interactions between EC and VSMC in the inflammatory processes involved in diabetes and emphasizes the role of vitamin D in the inflammatory response. The use of different donors strengthens the significance of our findings showing that genetic variations do not affect the impact of vitamin D on the expression of inflammatory-related proteins in our model.