A process for producing an .alpha.-arylalkanoic acid ester represented by the general formula ##STR1## wherein Ar represents an aryl group which may optionally be substituted, and R.sup.1 and R.sup.2, independently from each other, represent a lower alkyl group,which comprises reacting a Grignard reagent prepared from an aryl halide of the general formulaAr--X.sup.1 (II)wherein Ar is as defined above and X.sup.1 represents a halogen atom,and magnesium, with an .alpha.-haloalkanoic acid ester of the general formula ##STR2## wherein R.sup.1 and R.sup.2 are as defined above, and X.sup.2 represents a halogen atom,said reaction of the Grignard reagent with the .alpha.-haloalkanoic acid ester of general formula (III) being carried out in the presence of a nickel compound.