Measurements of the elastic constants c33, c44, and c66 in FeCl2 are reported. The temperature dependence of c44 and c66 in the paramagnetic region is explained by the strain-single-ion coupling mechanism. Similar effects were previously observed for rare-earth ions but not for transition metal ions. The effect of this coupling for c33 is expected to be small and was not observed experimentally. A critical behavior of c33 is observed near the Néel temperature.