Physical effects induced in micro-convective gaseous slip-flow due to variation in fluid properties are numerically examined in this paper. The problem is particularly simulated for slip-flow through a micro-channel heat sink (MCHS) having constant heat flux supplied from the wall under hydrodynamically and thermally fully developed flow (FDF) conditions. It is observed that the Nusselt number (Nu) for slip-flow is significantly higher than the no-slip-flow condition and Nu is significantly affected due to variable fluid properties (VFP). Four different cases of VFP are studied in order to investigate their effects individually. Pressure and temperature dependent density (ρ(p, T)) variation flattens the axial velocity profile in radial direction (u(r)) profile which promotes faster-moving particles close to the wall which considerably enhances Nu. The incorporation of temperature-dependent viscosity (μ(T)) variation marginally enhances Nu along the flow. Incorporation of temperature-dependent thermal conductivity (k(T)) variation highly augments Nu due to higher ρ and higher k fluid near to the wall and the incorporation of temperature-dependent specific heat at constant pressure (Cp(T)) variation reduces Nu due to lower k fluid near to the wall. The investigation also shows that the pressure drop significantly deviates from no-slip to slip condition. Furthermore, the effects of VFP on the gauge static pressure drop (Δpg) and slip velocity are also examined. The incorporation of μ(T) and k(T) variations trivially affects the Δpg and slip velocity. However, the incorporation of Cp(T) variation significantly affects the Δpg and slip velocity.