Background: Tissue-engineered vascular grafts (TEVGs) offer potential to overcome limitations of current approaches for reconstruction in congenital heart disease by providing biodegradable scaffolds on which autologous cells proliferate and provide physiologic functionality. However, current TEVGs do not address the diverse anatomic requirements of individual patients. This study explores the feasibility of creating patient-specific TEVGs by combining 3-dimensional (3D) printing and electrospinning technology. Methods: An electrospinning mandrel was 3D-printed after computer-aided design based on preoperative imaging of the ovine thoracic inferior vena cava (IVC). TEVG scaffolds were then electrospun around the 3D-printed mandrel. Six patient-specific TEVGs were implanted as cell-free IVC interposition conduits in a sheep model and explanted after 6 months for histologic, biochemical, and biomechanical evaluation. Results: All sheep survived without complications, and all grafts were patent without aneurysm formation or ectopic calcification. Serial angiography revealed significant decreases in TEVG pressure gradients between 3 and 6 months as the grafts remodeled. At explant, the nanofiber scaffold was nearly completely resorbed and the TEVG showed similar mechanical properties to that of native IVC. Histological analysis demonstrated an organized smooth muscle cell layer, extracellular matrix deposition, and endothelialization. No significant difference in elastin and collagen content between the TEVG and native IVC was identified. There was a significant positive correlation between wall thickness and CD68(+) macrophage infiltration into the TEVG. Conclusions: Creation of patient-specific nanofiber TEVGs by combining electrospinning and 3D printing is a feasible technology as future clinical option. Further preclinical studies involving more complex anatomical shapes are warranted.