Mulyosari roundabout becomes the liaison of residential area, education and shopping center in Mulyosari and surrounding areas. The construction of new activity centers in the region brings consequences to the increased volume of vehicles in the Mulyosari Roundabout. In this paper will be presented evaluation results on the performance of Mulyosari roundabout. The data used include geometric data, traffic flow, environmental conditions, location map, population number, and growth of motor vehicles. Further analyzed in accordance with existing methods in MKJI 1997 with the help of KAJI program to calculate the volume on the existing condition. Results obtained in 2017 obtained DS> 0.75 on one part of the roundabout, so that the performance changes to be a signal intersection. With the improvement to 3 phases, obtained DS> 0.75 on all approaches and Level of Service (LOS) intersection is C. While in the projection of 2019-2021 obtained LOS D, then in 2022 obtained LOS E.