A concentration series of sodium–gadolinium molybdate single crystals have been grown by the Czochralski method from melts of stoichiometric and some nonstoichiometric compositions in atmospheres with different oxygen contents. The actual compositions, microhardness, and crack resistance of the grown crystals have been investigated. All crystals are characterized by a significant sodium deficit with respect to stoichiometry and a large number of vacancies in the (Na + Gd) sublattice. The range of congruent melting is determined for this compound, and its homogeneity range is estimated to extend (on the scale of atomic concentration ratios Gd/Na) at least from 1.10 to 1.75. It is found that the microhardness of sodium– gadolinium molybdate crystals is significantly anisotropic, whereas the degree of crack resistance anisotropy does not exceed the measurement error. At the same time, neither microhardness nor crack resistance exhibit any significant dependence on the growth charge composition and the synthesis conditions in the investigated range of variation in these parameters.