The gaseous PVTx properties of trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) + 1,1-difluoroethane (R152a) mixtures are measured at temperatures from 285.15 to 310.15 K in 5 K intervals, pressures of up to 0.8 MPa, and compositions of R1234ze(E) from 0.35 to 0.55 mass fraction using the Burnett isothermal expansion method. The uncertainties in the experimental device are estimated to be within +/-10 mK for temperature, +/-4.0 kPa for pressure, and +/-0.3% for mass fraction. The densities and compressibility factors for each mixture are obtained, and the second and third virial coefficients of the gas virial EOS are fitted on the basis of experimental PVTx data. The relative errors between the calculated pressure from the fitted gas virial EOS and the experimental data of this study are within +/-0.6%.