The development of two-phase cooling for both two-dimensional (2D) and three-dimensional (3D) integrated circuits using pumped dielectric coolant has gained recent attention due to the ability to manage high heat densities, compatibility with electronics and low cooling energy usage. Development of this approach requires high fidelity and computationally manageable conjugate thermal models both at the device level as well as the system level. Recent studies have shown micro-scale modeling of in-situ thermal and hydrodynamic phenomena (e.g. boiling and bubble dynamics) of two-phase flow boiling with good accuracy. This paper describes a simulation tool named Sim2Cool which addresses the need for macro-scale system level design simulation for two-phase cooling. The Sim2Cool simulation tool uses an enthalpy-based / energy balance model for the system components and a reduced order model for device-level model. The system simulator tool allows system component parameters to be quickly analyzed including; condenser, reservoir and tubing diameter as well as heat dissipation and flow rate to quantify the impact on the system coefficient of performance (COP). Such tools are critical to accelerating the integration of two phase cooling with microelectronics to realize performance gains by way of high density electronic packaging as Moore's law on silicon technology advancement reaches physics limits.