Background: Immune checkpoint inhibitors (ICIs), particularly programmed death-ligand 1 (PD-L1) inhibitors such as atezolizumab, have significantly improved outcomes in cancer therapy. However, these agents may cause immune-related adverse effects, including nephrotoxicity associated with oxidative stress and cellular stress responses. This study aimed to investigate and comparatively evaluate the protective effects of adenosine triphosphate (ATP) and taxifolin against atezolizumab-induced renal tissue injury in rats. Methods: Animals were divided into four groups: healthy (HG), atezolizumab (ATZ), ATP + atezolizumab (ATAZ), and taxifolin + atezolizumab (TXAZ). ATP (4 mg/kg, i.p.) and taxifolin (50 mg/kg, oral) were administered for six days, while atezolizumab (10 mg/kg, i.p.) was given on days 1 and 4. On day 7, renal tissues were collected for biochemical, histopathological, and double immunofluorescence analyses. Results: Atezolizumab significantly increased malondialdehyde (MDA) levels and decreased total glutathione (tGSH), superoxide dismutase (SOD), and catalase (CAT) levels, indicating enhanced oxidative stress and impaired antioxidant defense. These changes were accompanied by tubular degeneration and increased expression of apoptotic markers. Both ATP and taxifolin significantly ameliorated these alterations; however, ATP demonstrated a more pronounced protective effect. Conclusions: In conclusion, ATP and taxifolin attenuated the biochemical, histopathological, and immunofluorescence alterations associated with atezolizumab administration. ATP exhibited a more pronounced protective effect than taxifolin under the conditions of this experimental model. Nevertheless, further experimental studies are required to elucidate the mechanisms underlying these effects.