In recent years we are faced with the growing trend of illegal buildings (IBs) construction in urban areas as the urban population and expansion have been significantly increased. Field check, as the currently used method of IB detection in Iran is time, cost and man power consuming and it may be ended in some collusion between the municipality inspectors and constructors. In this research, a semi-automatic method of IB detection based on an integrated remote sensing and GIS change detection method, using two-temporal satellite images of west of Tehran, the urban maps at the scale of 1:2000 and an up to date municipality property database containing building information, is proposed. In the pre-processing step, firstly the radiometric and geometric corrections have been applied to the images. Then, the changed pixels were detected using a conflation of fuzzy XOR operator and intuitionistic fuzzy implication methods. Afterward, the change percentage of each building was calculated using some spatial analyses and was compared with the standard construction threshold of municipality study area. Therefore, the buildings which were under construction were detected. In the next step, the IBs were detected as a suspected point undertaking a query to the municipal database. Finally, the existence of authenticity of IBs was checked undertaking a field visit from the suspected point. The results of this research verified that from the 338 buildings detected in the image, 16 buildings were detected as under construction and 2 buildings detected as illegal buildings, respectively. Furthermore, the overall accuracies of 98%, 86% and 100% were obtained for the fuzzy-based image classification, detection of under construction buildings and IBs detection, respectively.