The Mass Timber Panel-Concrete (MTPC) composite floor system considered in this paper consists of a Mass Timber Panel (MTP) connected to reinforced concrete slab with Self-Tapping Screw (STS) connector and a sound insulation layer in between. This type of composite floor system is intended for mid- to high-rise building applications. Two types of MTPs with normal weight concrete, two insulation thicknesses, two screw embedment lengths and two screw angles were investigated through connection tests to characterize connection stiffness and strength. The main goal of this connection test program was to provide preliminary test data to assist in the development of a model to predict connections lateral stiffness and strength under consideration of insulation thickness, screw angle, withdrawal and embedment properties of screws in MTP. Connection test results show that screws at an insertion angle of 30° have a higher stiffness and strength along with a larger embedment length compared to the screws at a 45° angle and smaller embedment length. Stiffness seemed to be more susceptible to the influence of presence of insulation compared to strength with 40-65% reduction of stiffness and 10-20% reduction of strength were noticed for an insulation thickness of 5 mm. Screws in CLT showed higher strength while screws in CLP showed higher stiffness but the difference is insignificant.