Three new letrozole complexes {[Cu(Le)4Cl2]·(H2O)} (1), {[Ni(Le)4Cl2]·(H2O)}(2) and {[Co(Le)4Cl2]·(H2O)} (3) (Le = letrozole = 1‐[bis(4‐cyanophenyl)methyl]‐1, 2, 4‐triazole) were obtained from self‐assembly of CuCl2, NiCl2·6H2O, and CoCl2·6H2O with medicine letrozole. All compounds were characterized by IR spectroscopy, elemental, single‐crystal as well as powder X‐ray diffraction, and thermogravimetric analyses. The analyses of the structures indicate that all crystals belong to monoclinic system, space group C2/c, for complex 1 with crystal data a = 34.501(18) Å, b = 12.724(7) Å, c = 16.116(9) Å, β = 114.958(7) °, V = 6414(6) Å 3, Z = 4, F(000) = 2660, R1 = 0.0668, wR2 = 0.1574; for complex 2, a = 34.769(6) Å, b = 12.7267(18) Å, c = 16.046(2) Å, β = 115.281(3) °, V = 6420.1(16) Å 3, Z = 4, F(000) = 2656, R1 = 0.0510, wR2 = 0.0896; for complex 3, a = 35.063(8) Å,b = 12.658(3) Å, c = 16.056(4) Å, β = 115.387(3) °, V = 6438(2) Å3, Z = 4, F(000) = 2652, R1 = 0.0528, wR2 = 0.1205. The local arrangements around central metal atoms (CuII, NiII, and CoII) can be best described as distorted octahedra which are constructed by two chlorine atoms and four monodentate nitrogen atoms from different letrozole ligands. XRD results of 1–3 show that all peaks displayed in the measured patterns at room temperature closely match those in the simulated patterns generated from single‐crystal diffraction data, indicating single phases of 1–3 were formed.