The bromination reaction of 1,2,3,4-tetrahydro-1,10-phenanthroline (tphen) is investigated, which can afford a new heterocyclic compound, namely 6-bromo-1,2,3,4-tetrahydro-1,10-phenanthroline (1). The bromide salt of 1, i.e., 1 · (1H) · Br (2), can be isolated from the bromination system. The accurate structures of both compounds are confirmed and investigated by single-crystal X-ray diffraction. The result proves that the bromination reaction of tphen mainly affords its C6-substituted product. In compounds 1 and 2, the N−H···Br hydrogen bonds play an important role in intermolecular connection. Crystal data of 1: Monoclinic system, sp. gr. Pc, a = 4.6628(8) A, b = 8.7980(15) A, c = 13.1347(19) A, β = 101.342(5)°, Z = 2, V = 528.31(15) A3. Crystal data of 2: Monoclinic system, sp. gr. P21/n, a = 16.6171(16) A, b = 7.8323(8) A, c = 18.6972(18) A, β = 113.597(2)°, Z = 4, V = 2230.0(4) A3.