We have studied the evolution of grid turbulence in a planar contraction by focusing on the flow at the centre symmetry plane. Measurements are carried out in water with inlet Taylor-microscale Reynolds number varying from 51 to 99. Detailed laser-Doppler anemometry measurements show that the streamwise fluctuating velocity component for contraction ratio $C\,{<}\,2.5$ closely follows the decay of grid turbulence in a straight channel. Furthermore, the turbulent kinetic energy reaches a minimum value in the range of contraction ratio $1.5\,{<}\,C\,{<}\,2.5$. Turbulent intensity, independent of contraction angle and Reynolds number, decays exponentially. The results show that the flow reaches its peak of anisotropy at $2.5\,{<}\,C\,{<}\,3.5$ and then returns to a nearly fully isotropic state inside the contraction. The return to isotropy within the contraction is attributed to the rapid part of the pressure–strain correlation term in the transport equation of the Reynolds-stress anisotropy tensor.