Collagen-based biomaterials are a viable option for tendon reconstruction and repair. However, the weak mechanical strength of collagen constructs is a major limitation. We have previously reported a novel methodology to form highly oriented electrochemically aligned collagen (ELAC) threads with mechanical properties converging on those of the natural tendon. In this study, we assessed the in vivo response of rabbit patellar tendon (PT) to braided ELAC bioscaffolds. Rabbit PTs were incised longitudinally and the ELAC bioscaffold was inlaid in one limb along the length of the tendon. The contralateral limb served as the sham-operated control. Rabbits were euthanized at 4 or 8 months postoperatively. High-resolution radiographs revealed the absence of ectopic bone formation around the bioscaffolds. Four months post-implantation, the histological sections showed that the ELAC bioscaffold underwent limited degradation and was associated with a low-grade granulomatous inflammation. Additionally, quantitative histology revealed that the cross-sectional areas of PTs with the ELAC bioscaffold were 29% larger compared with the controls. Furthermore, ELAC-treated PTs were significantly stiffer compared with the controls. The volume fraction of the tendon fascicle increased in the ELAC-treated PT compared with the controls. By 8 months, the ELAC bioscaffold was mostly absorbed and the enlargement in the area of tendons with implants subsided along with the resolution of the granulomatous inflammation. We conclude that ELAC is biocompatible and biodegradable and has the potential to be used as a biomaterial for tendon tissue engineering applications. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 100B: 400–408, 2012.