DSF buildings have been designed and used mainly for the purposes of improving human comfort and decreasing energy consumption in new and renovated structures. However, there has been scarce studies in literature concerning daylighting in DSF buildings in comparison to thermal and ventilation systems. Actually, lighting is responsible for %30 to %40 of all the energy utilized in office buildings. This value is remarkable to take into consideration the daylight efficiency of DSF building at the design phase. This study examines the effect of double-skin facades system variables on daylight performance. In accordance with this purpose, an office in Izmir Institute of Technology (Iztech) has been selected and primarily, it has been tested to measure the reliability of the daylight simulation software (Relux) to be used. Later, the effect of the second skin on daylight performance has been analyzed by comparing single skin glass curtain wall and double skin facade simulations. Various components generally used in the double-skin facades have been detected and their effects on daylight level have been studied. These components are glass types, replacement of internal and external facade layers and the depth of cavity. The simulation findings have been distributed to various comparison groups and the ratios of meeting 300 lx – 500 lx value suggested in office buildings have been analyzed. When the obtained results are examined, it can be understood that the daylight can be used at an optimal level with some interventions that can be applied in the design process of the double-skin facades.