[en] Axelrod's model in the square lattice with nearest-neighbors interactions exhibits culturally homogeneous as well as culturally fragmented absorbing configurations. In the case in which the agents are characterized by F = 2 cultural features and each feature assumes k states drawn from a Poisson distribution of parameter q, these regimes are separated by a continuous transition at $q_c=3.10\pm <!--\; ??\; -->0.02$. Using Monte Carlo simulations and finite-size scaling we show that the mean density of cultural domains μ is an order parameter of the model that vanishes as $\mathrm{\mu <!--\; ??\; -->}\sim <!--\; ???\; -->(q-<!--\; ???\; -->q_c{)}^{\mathrm{\beta <!--\; ??\; -->}}$ with $\mathrm{\beta <!--\; ??\; -->}=0.67\pm <!--\; ??\; -->0.01$ at the critical point. In addition, for the correlation length critical exponent we find $\mathrm{\nu <!--\; ??\; -->}=1.63\pm <!--\; ??\; -->0.04$ and for Fisher's exponent, $\mathrm{\tau <!--\; ??\; -->}=1.76\pm <!--\; ??\; -->0.01$. This set of critical exponents places the continuous phase transition of Axelrod's model apart from the known universality classes of non-equilibrium lattice models. (letter)