Potatoes, commercially treated with thiabendazole, tecnazene and chlorpropham, were processed into potato crisps and jacket potato crisps at a crisp factory using standard manufacturing conditions. A multi‐residue method based on gas chromatography with mass spectrometric detection was developed and used to determine pesticide residue levels in the potatoes and potato crisps. Results showed that the residues of all three pesticides were significantly reduced to less than 2% and less than 10% of the maximum theoretical residue carry‐through level for potato crisps and jacket potato crisps respectively.