Simultaneous measurements of instantaneous velocity and concentration fields were conducted using particle imaging velocimetry (PIV) and planar laser-induced fluorescence (PLIF) for the diffusion field of passive scalar in a round jet discharging into uniform counter-flow. Axial profiles of the concentration statistics along the jet centerline showed that both rms concentration fluctuation and axial turbulent flux of scalar have two certain peaks in the near field of the jet and in the mean stagnant region. It was also suggested that the absolute value of radial turbulent flux has a tendency to increase in the region where the counter flow deflects around the dividing stream surface.