Oxidative stress is a key element of ischemia–reperfusion injury, occurring during kidney preservation and transplantation. Current options for kidney graft preservation prior to transplantation are static cold storage (CS) and hypothermic machine perfusion (HMP), the latter demonstrating clear improvement of preservation quality, particularly for marginal donors, such as extended criteria donors (ECDs) and donation after circulatory death (DCDs). Nevertheless, complications still exist, fostering the need to improve kidney preservation. This review highlights the most promising avenues of in kidney perfusion improvement on two critical aspects: ex vivo and in vitro evaluation.