Percutaneous osseointegrated implants offer significant benefits to amputees, including improved mechanical feedback and reduced skin irritation. However, their percutaneous nature increases susceptibility to biofilm-associated infections. This study evaluated the potential efficacy of antimicrobial blue light (aBL) as a preventive strategy to manage biofilm burden in a 12-week ovine model wherein two treatment cycles were implemented. In this study, aBL was applied proactively to reduce surface colonization and prevent infection progression, rather than to treat confirmed or deep infections. Sheep were inoculated with Staphylococcus aureus biofilm and treated with aBL or systemic antibiotics, with or without a washing protocol. aBL with washing achieved the greatest bacterial reduction, lowering CFU levels to 3.0 ± 0.3 log₁₀ during the second treatment period, significantly outperforming washing alone, which resulted in 5.6 ± 0.4 log10 (p < 0.05). The study also showed a lower observed infection rate (14% vs. 43%), when comparing aBL with washing to washing only based on histologic, microCT, and gross assessments, though no statistical comparison was performed. Despite these benefits, the aBL treatments induced notable tissue changes, including increased epithelial thickening, rete ridge elongation, and accelerated skin/tissue downgrowth. Systemic antibiotics were effective during the initial treatment period but failed to reduce biofilm burden during the second treatment cycle. Altogether, while aBL combined with washing shows promise as a localized preventive therapy for reducing biofilm burden and implant-related infection, the observed tissue remodeling and accelerated downgrowth highlight the need for further investigation to ensure long-term safety.