Decontamination of sensitive equipment materials contaminated by organophosphorus (OP) compounds by a two-stage process was evaluated. The process involved extraction of OP from contaminated materials with methanol (first stage), followed by decomposition of OP by heterogeneous catalytic methanolysis (second stage). In a series of tests diazinon, malathion, paraoxon, parathion, and other organophosphorus pesticides were spiked onto sensitive equipment materials and extracted with methanol after a presented contact time. After extraction, the lowest quantity of residue was found for diazinon, while parathion was the most persistent. High-impact polystyrene (HI-PS) retained 10-fold or more mass of OP than other tested materials. The surface of the HI-PS was deteriorated after contacting with OP due to a plasticizing effect. A longer contact time with HI-PS and lower polarity factor of OP resulted in higher residual amounts of OP after extraction. In the second stage of the process, diazinon and paraoxon were decomposed by methanolysis in presence of palladium- and ytterbium-based solid-supported catalysts, respectively. Complete destruction of diazinon was achieved within 30 s, while 60 min was required to destroy paraoxon.