Current methods for closure of congenital diaphragmatic hernia using patches are unsatisfactory, and novel collagen-based scaffolds have been developed, and successfully applied in a rat model. However, for translation to the human situation constructs must be evaluated in larger animal models. We developed collagen scaffolds enforced with Vicryl, loaded either with or without the muscle stimulatory growth factor insulin-like growth factor 1 (IGF1). We describe our steps to a surgical method to implant these scaffolds into a diaphragmatic defect in 1.5–3 week old lambs, and evaluate the scaffolds 6 months after implantation. Omentum was attached to the scaffold. At sacrifice, eventration of the implantation site was observed in all animals with a thin layer of tissue separating the abdomen from the thorax. Histologically, no scaffold remnants could be observed. Fatty tissue surrounded by fibrous tissue was seen, resembling encapsulated omentum, with collagen-rich tissue present between this tissue and the original diaphragmatic muscle. Outcomes were not different for scaffolds with or without IGF1. In conclusion, the scaffolds integrated well into the surrounding tissue, but slower degrading materials are needed to prevent eventrations. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 102B: 756–763, 2014.