In the crystal structure of the title compound, 2C(2)H(7)N(2) (+)·SO(4) (2-), which contains four cations and two anions in the asymmetric unit, the ions are inter-connected by an extensive hydrogen-bonding system whereby two of the O atoms of sulfate ion are hydrogen-bonded to the amidinium H atoms of two cations, leading to the formation of two eight-membered rings. The two remaining O atoms inter-connect two H atoms of acetamidinium cations, forming an infinite chain. The C⋯N separations within the H(2)N⋯C⋯NH(2) moieties are similar, with an average value of 1.305 (2) Å, which is in good agreement with a delocalization model.