This study examined the protective effects of Spirulina platensis (SP) on African cat fish (Clarias gariepinus) against ultraviolet radiation-A (UV-A) induced oxidative stress, immunotoxicity, and histological damage. Recognized for its nutritional value and envi ronmental benefits, SP was evaluated as a potential bioremediation agent. The experiment involved four groups: a control group, a UV-A-exposed group, a UV-A + 100 mg/L SP group, and a UV-A + 200 mg/L SP group, with UV-A exposure for 1 h daily over 3 days. Serum markers of oxidative stress (superoxide dismutase (SOD), total antioxidant capac ity (TAC), and malondialdehyde (MDA)) and immune responses (lysozyme (LYZ) and phagocytic activity (PhA)) were measured. UV-A exposure significantly decreased SOD and TAC levels and increased MDA levels. However, SP treatment countered these effects, raising SOD and TAC levels while lowering MDA levels in both SP-treated groups. Simi larly, the UV-A-induced reduction in LYZ and PhA activities was reversed by SP treatment, returning to near control levels. Histological analysis showed substantial tissue damage in UV-A-exposed fish, which was mitigated in SP-treated groups, with higher SP concentra tions offering greater protection. These results suggest that SP effectively reduces oxidative stress, boosts immune responses, and preserves tissue integrity in UV-A-exposed African catfish. Overall, this study highlights the potential of SP as a valuable bioremediation agent in aquaculture, promoting fish health and resilience to environmental stressors. SP emerges as a promising candidate for enhancing sustainable aquaculture practices through its pro tective and ameliorative properties.