In times of progressive urbanization and increased environmental awareness, the mobility sector faces the challenge to satisfy an increasing demand, while simultaneously decreasing the negative externalities of transportation. The emerging concept Mobility as a Service (MaaS) claims to resolve this conflict, by offering individualized and seamless mobility through combination of all available modes. This thesis quantifies the tank to wheel (TTW) greenhouse gas (GHG) emissions of a MaaS implementation and simulates effects of potential variations in the service. The pilot under focus is an alteration of MaaS, which is exclusively available to the work force of a specific corporation. This variation is called Corporate Mobility as a Service (CMaaS). The evaluation is based on cross-sectional survey among the employees and operational data from the CMaaS operator. The transport demand model applies a person category approach. The total daily GHG emitted by the work force’s on-site mobility is estimated to 3.735 tCO2. Compared to on-site trips by private cars, trips with CMaaS emit less than half as many GHG emissions per passenger kilometer traveled. This highlights the environmental benefits of MaaS, especially in replacing short trips by private car. Due to the composition of the underlying data sources and the therefore chosen methodology the reactivity to implemented scenarios is very limited. Thus, analysis and interpretation of the results is restricted to largely aggregated levels. Nonetheless, this study offers an initial orientation point for further estimation of TTW GHG emissions by MaaS schemes. Beyond, it highlights the lack in understanding and modelling of corporate mobility in general.