AbstractBased in the phase equilibrium study of the system Sm(C1O4)3‐4‐monochloroacetytantipyrine (C13H13ClN2O2)‐H2O at 30°C, we have synthesized the title complex [Sm(C13H13Cl‐N2O2)3(H2O)4](ClO4)3‐4H2O. The single crystal structure analysis on RASA‐IIS Rigaku diffractometer shows that the coordination number of the metal ion is nine and the geometry of the complex is tricapped trigonal prism. Two of the three molecules of organic ligand act as bidentate chelated through both carbonyl oxygens to the metal ion, but the other one as a monodentate coordinated only through the ring carbonyl oxygen, the side chain carbonyl is far away from the central ion. The crystal is monoclinic, space groupP21, α = 18.013(4),b= 14.709(3),c= 10.536(3) Å, β=94.69(2)°,