The photocatalytic activity of Mn doped TiO₂ for the ozonation of tetradifon pesticide in aqueous solution was studied. Various loadings of catalysts Mn/TiO₂ (1%, 2.5% and 5%) was prepared and characterized by standard analytical techniques. Photocatalyzed ozonation with 2.5% Mn/TiO₂ yielded 100% degradation and mineralization of tetradifon in 2.0 h under basic pH conditions. The extent of degradation of tetradifon pesticide and its mineralization were confirmed by GC-MS. For 10 mg/L of tetradifon, 0.1 g L⁻¹ of catalyst was found to be the optimum for effective mineralisation. The reused experiment confirmed that Mn/TiO₂ kept a good photocatalytic activity and stability, and it was a promising heterogeneous catalyst. The catalyst is fully recoverable and reusable multiple times with no loss of activity.