The success of cardiovascular implants is associated with the development of an endothelium on material surface, critical to the prevention of intimal hyperplasia, calcification and thrombosis. A thorough understanding of the interaction between vascular endothelial cells and the biomaterial involved is essential in order to have a successful application which promotes healing and regeneration through integration with native tissue. In this study, we have developed collagen immobilized nanostructured surfaces with controlled arrays of high aspect ratio nanowires for the growth and maintenance of human microvascular endothelial cells (HMVECs). The nanowire surfaces were fabricated from polycaprolactone using a novel nanotemplating technique, and were immobilized with collagen utilizing an aminolysis method. The collagen immobilized nanowire surfaces were characterized using contact angle measurements, scanning electron microscopy and X-ray photoelectron spectroscopy. Human microvascular endothelial cells were used to evaluate the efficacy of the collagen immobilized nanowire surfaces to promote cell adhesion, proliferation, viability and differentiation. The results presented here indicate significantly higher cellular adhesion, proliferation and viability on nanowire and collagen immobilized surfaces as compared to the control surface. Further, HMVECs have a more elongated body and low shape factor on nanostructured surfaces. The differentiation potential of collagen immobilized nanowire surfaces was also evaluated by immunostaining and western blotting for key endothelial cell markers that are expressed when human microvascular endothelial cells are differentiated. Results indicate that expression of VE-cadherin is increased on collagen immobilized surfaces while the expression of von Willebrand factor is statistically similar on all surfaces.