Effect of 100 MeV58Ni+8 ion irradiation on the electrical transport behaviour of Al-Cu-Fe quasicrystalline thin films have been investigated by in situ and ex situ resistivity measurements. The quasicrystalline thin films grown by indirect heating, electron-beam and flash evaporation methods have been used for this purpose. The fluence of 100 MeV58Ni+8 beam is varied from 1 × 109 to 1 × 1013 particles/cm2. A small oscillatory variation of resistivity up to a critical fluence of 5×1012 particles/cm2 is observed in all the samples. A rapid decrease in resistivity is observed at a fluence of 1 × 1013 particles/cm2 for all the quasicrystalline thin films. These thin films also show negative temperature coefficient of resistivity similar to that of unirradiated quasicrystalline thin films. The results of simulation for resistivity versus temperature (unirradiated and irradiated at fluence 1 × 1013 particles/cm2) support the observed behaviour of resistivity with temperature. © 2002 Elsevier Science Ltd. All rights reserved.