Iraq has witnessed a series of wars and was subject to severe destruction, particularly after its invasion and occupation in 2003. In Light of the current economic situations in Iraq, optimal utilization of resources has become a pressing need. This study aims at using Integer Linear Programming for mathematical model in urban development, taking constructing new houses in Iraq as a case study. A mathematical model for the optimal distribution of sub-contractors to execute (170) proposed houses with different area (150,180, 200, 250, 300 m²) and two execution levels (first degree and second degree) has been built, with the aim of minimizing costs and realizing the project within the planned time period. Data was collected from the tenders of six sub-contractors, including unit price according to area and execution level, as well as the time period for unit accomplishment. Seven mathematical for seven case studies were used for sensitivity analysis. Through changing the available resources and requirements, the form of the constraints changed, where some decision variables and competition constraints were excluded and new constraints were added. Integer Linear Programming was employed in solving the mathematical model equation with the aid of (Linprog) software. The results showed the possibility of applying mathematical modeling and Integer Linear Programing effectively to achieve minimum execution cost within the planned time period, and optimum assignment of sub-contractor. Furthermore, the study finding revealed enabling the project manager or work owner to select the optimal solution according to the company's requirement. The researcher recommends to expand using mathematical modeling for solving problems in construction projects.