A series of Ni-doped SnO2 nanorods with controlled morphology and surface composition were obtained via post-synthetic hydrothermal treatment. A comprehensive characterization combining advanced physicochemical methods and computational modeling was employed to investigate their formation and growth within the oriented attachment (OA) framework. High degradation rates of mixed dye pollutants were achieved in real river water, underscoring the photocatalyst’s robustness and practical applicability. These results highlight the pivotal role of and OA-driven growth in tuning photocatalytic activity, confirming the material’s potential for efficient multipollutant removal under environmentally relevant conditions.