The interaction of MoS2 single-layer dispersion with 1,10-phenanthroline has been studied over the pH range 0-11. Only protonated phenanthroline initiates flocculation of dispersion and formation of intercalation compounds. Two intercalated phases containing respectively 0.31-0.35 and 0.1 mol of phenanthroline per mol MoS2 have been isolated. In the first one (interlayer spacing c = 14.92-15.56 Angstrom) the planar organic species are inclinated with respect to MoS2 layers. In the second one (c = 9.7 Angstrom) these moieties are oriented parallel to the layers.