The experiments are conducted to investigate the effect of temperature, magnetic field, and nanoparticles on the effective thermophysical properties (thermal conductivity, viscosity and density) of the magnetic nanofluids. The Fe3O4 magnetic nanoparticles are dispersed in the water at various concentrations and the resulted suspensions are assessed in the temperature range 10–70°C and under the presence of an external magnetic field range from 0 to 750 Gauss. The different parameters have observed the significant effects on the thermal conductivity, viscosity and density of these colloidal suspensions. The experiments have revealed that the thermal conductivity is enhanced with nanoparticle concentration, temperature and magnetic field. The new empirical correlations using Buckingham-Pi theorem and analytical approach have been proposed and discussed comprehensively for the effective thermal conductivity for such magnetic suspensions under the presence of a magnetic field. The viscosity of the colloidal suspension is shown significant enhancement with nanoparticle concentration and decrement with increasing temperature. The empirical correlation for the viscosity is reported and elucidates the temperature dependence of the viscosity. However, the density for these suspensions shows only a trivial enhancement with concentrations.