OBJECTIVES: To determine the effects of implanting a novel mosaic tissue-engineered porcine pulmonary artery valved conduit into the right ventricular outflow tract of sheep at a long-term follow-up. METHODS: The designed mosaic tissue-engineered porcine pulmonary artery valved conduits were implanted between the right ventricular outflow tract and distal pulmonary artery in sheep using the off-pump method. The sheep weight, conduit diameter, pulmonary valve annular diameter, left ventricular end-diastolic diameter, calcification and regurgitation of the pulmonary valve were measured preoperatively and at 6 and 12 months postoperatively. Macroscopic observation, ultrastructural analysis, endothelialization and detection of calcium content were performed after sacrificing the sheep at 12 months after surgery. RESULTS: The average sheep weight at 12 months after surgery was significantly higher than that preoperatively (P < 0.05), indicating that the sheep continued to grow well. The transplanted conduit showed unobstructed blood flow, soft walls and a smooth inner wall, but no ectasia or stenosis. The valve of the conduit was partially stiff, able to open and close and mild-to-medium regurgitation was present. The conduit diameter, pulmonary valve annular diameter and the left ventricular end-diastolic diameter were each significantly increased (P <0.05). Haematoxylin-eosin staining and scanning electron microscopy revealed regularly arranged cells with slight inflammatory cell infiltration and a clear, fibrous texture. Immunohistochemical staining indicated that endothelial cell marker CD31-positive cells had formed a continuous film-like structure on the inner wall of the conduit. Scattered smooth muscle actin-positive cells were found in the middle layer of the conduit. CONCLUSIONS: The mosaic tissue-engineered porcine pulmonary artery valved conduit demonstrated good biocompatibility, did not cause an immune rejection response, contributed to endothelial coverage and has the potential to adapt to the needs of the growth and development of the body.