The aim of this study is to determine the performance of the Balçova . Narlıdere District Heating System and to reveal the critical points. During this study, with the help of Balçova Jeotermal Company.s database, Balçova . Narlıdere Geothermal District Heating System is simulated in Pipelab Geothermal District Heating System simulation program and the pressure and temperature distributions of the system are determined. In the light of these analyses, the critical points of the Balçova . Narlıdere Geothermal District Heating System are pointed out with the possible reasons and solution alternatives are discussed. Meanwhile, with the flow meters which are assembled to two apartment buildings chosen in the system, the amount of the fluid and the energy consumed by the users are observed. The observed values are compared with the calculated values according to the outdoor temperatures.