One of the most complex issues of urban planning is informal settlement which is a multidimensional phenomenon with multiple indices. The spatial growth of informal settlements is affected by complex internal and external drivers. Combined use of GIS and agent based model as an approach of this research might be an adequate strategy for modeling these process. The purpose of this study is modeling informal settlement growth of the phenomenon on a cadastral scale in vector GIS, using land parcel agents and decision maker agents. Two scenarios were considered for defining the neighborhood effects and results of modeling were investigated and were evaluated for these scenarios. In this model decision maker agents as moving agents include people who are working in the downtown core and those who are working in industrial suburb areas.They search the surroundings to find suitable land for housing. Land parcel agents as immobilizing agents calculate their total suitability using spatial factor based on the preferences of decision maker agents. The proposed model was implemented on one of the informal settlements districts in the city of Kashan, Isfahan province, Iran. Evaluating results with actual data indicated that the proposed model was able to predict the informal settlements growth with 86% overall accuracy. This study indicated that although the developed neighboring numbers are important to develop a land parcel on cadastral scale, but developed neighborhood areas have a greater role than their numbers. The findings of this research also indicate that developed parcels located within the radius of 120 meters of a target land parcel have different effects on the development of target parcel proportional to their distances.