Yogyakarta is one of cities in Indonesia with high population. Moreover, Yogyakarta is also known as student city due to many students come every year. As a result of the high increasing of population in this city so Yogyakarta has high traffic volume. SGM signalized intersection is one of intersection in Yogyakarta with high traffic volume that will be potential in causing traffic condition. Therefor this research aims to analyze and to model the the traffic occurred at SGM signalized intersection then estimating congestion cost. This research was conducted by surveying geometric condition, traffic volume, cycle time/phase of traffic light, and vehicle speed at intersection, then analyzing and modeling the traffic using Vissim 10 software with the indicators of queue and Level of Service (LOS). The indicators of congestion cost is value of vehicle, vehicle operation cost, spot speed, desired speed, value of time, and queue time. The performance of SGM signalized intersection assessed by LOS with F level at the peak hour is 06.30-07.30 WIB, so it is needed to evaluate and give the alternative solutions. Alternative 1 is changing the phase and alternative 2 is road widening. The result of existing analysis are queue of 92,48 second/vehicle with LOS F and congestion cost is Rp. 3.780.733,-/hour. Alternative 1 shows queue of 83,30 second/vehicle with LOS F and congestion cost is Rp. 3.703.258,-/jam. The improvement result from the models of alternative 2 are queue of 72,69 second/vehicle with LOS E and congestion cost is Rp. 3.265.934,-/hour.