An experimental study into the effect of background turbulence on the velocity field of a momentum-driven, axisymmetric, turbulent jet is presented. An approximately homogeneous, isotropic turbulent background with zero mean flow was generated by a Random Jet Array (RJA) in a water tank and is characterized by flying hot-film anemometry. Subsequently, velocity measurements of the jet evolution in quiescent and turbulent backgrounds were also performed using the flying hot-film anemometer. The results show that the background turbulence increases the rate of decay of the jet, which is expected to decrease the entrainment. Furthermore, the axial RMS turbulent velocity increases when external turbulence is present. Comparing the results with the literature and those of similar experiments measured using Acoustic Doppler Velocimetry (ADV), mean velocities are estimated relatively accurately by both techniques, while the ADV overestimates the RMS velocities.