This theoretical reactivity study was conducted on six molecules of a series of halogen-substituted Imidazole-Thiosemicarbazides (ITS) using density functional theory, at the B3LYP/6-31+G (d, p) level. Analysis of the thermodynamic formation quantities confirmed the formation and existence of the series of molecules studied. The study of the boundary molecular orbitals, including the energy gap (ΔE), electronegativity (), chemical hardness (η) and electrophilicity index (ω) provided a better overview of the molecular properties. Thus, the compounds ITS 1 and ITS 4 which have the lowest energy gaps between the boundary orbitals are the most reactive and the least stable. Furthermore, ITS 1 is the softest of the compounds studied. The analysis of the local descriptors and the isodensity map allowed us to identify the N14 nitrogen atom as the preferred electrophilic attack site and the C18 carbon atom as the preferred nucleophilic attack site. These electrophilic and nucleophilic attack sites (N14 and C18) are identical for all compounds according to the dual descriptors. Furthermore, halogen substitution on imidazole-thiosemicarbazides does not change the centres of reactivity. The dendrogram of the Hierarchical Ascending Classification Analysis allowed us to group all the six studied compounds into three categories. The most active one is ITS 3, ITS 2 and ITS 5 the moderately active compounds and ITS 1, ITS 4 and ITS 6, the least active ones. The surface profiler analysis showed us an almost smooth plane connecting the three (3) descriptors that are ΔE, ω and η. This result shows the linearity between these descriptors of reactivity.