The title salt, C(12)H(9)N(2) (+)·CH(3)O(4)S(-), contains an almost planar phenazinium cation [largest deviation from the least-squares plane = 0.040 (3) Å] and a methyl sulfate anion. The sulfate moiety of the latter is disordered over two sets of sites in a 0.853 (5):0.147 (5) ratio. In the crystal, the cations and anions are arranged alternately in layers parallel to (010). The cations pack along [100] with a tilt angle of 28.96 (4)° between this axis and the mean plane and are linked through inter-planar π-π inter-actions [shortest inter-planar distance = 3.421 (4) Å]. N-H⋯O hydrogen-bonding between the cations and anions is also observed.