The reaction of 3,4,5,6-tetrahydropyrimidine-2-thione (H(4)pymtH) with mercury(II) iodide in methanol in a 1:1 molar ratio resulted in the formation of single crystals of the title compound, [Hg(C(4)H(8)N(2)S)I(2)]. The Hg atom is coordinated by one S atom from H(4)pymtH at 2.456 (2) A and by two I atoms at distances of 2.6872 (7) and 2.7044 (6) A, and has a characteristic deformed trigonal coordination geometry. The molecule has crystallographic m symmetry but the Hg atom is disordered above and below the mirror plane.