A comprehensive study of the effect of Mg loading on the performances in Dry Reforming of Methane of a series of mesoporous Ni 6-Mg x-Al 2 O 3 catalysts containing 6 wt% Ni and 0 to 26 wt% Mg is presented. Complementary characterizations by N 2 sorption, XRD, SEM/TEM, FT-IR, H 2-TPR and H 2-TPD of the materials, synthesized by one-pot EISA method and studied in their calcined and reduced forms, reveal excellent porous ordering and high and homogeneous chemicals distribution up to an intermediate Mg content, afterwards MgO segregation occurs, associated to some structural loss, nickel sintering due to the disappearance of the stabilizing nickel aluminate species, and to strong basic sites formation. In line with these physicochemical changes, all catalytic results reveal the existence of volcano curves in which the optimum Mg content is between 5 and 10 wt%. This optimum is also discussed in view of turn over frequencies and activation energy values.