The millimeter-wave spectrum of the SiCl+ ion in the ground and first excited vibrational states was observed for the two isotopic (Cl-35 and Cl-37) species. The ion was generated in a free-space absorption cell by a hollow cathode discharge of SiCl4 diluted with He and discriminated from neutral species by the magnetic field effect on the absorption lines. The observed millimeter-wave spectrum was combined with a previously reported diode laser spectrum in an analysis to determine mass-independent Dunham coefficients as well as the mass scaling parameters. The equilibrium bond length of SiCl+ determined is r(e) = 1.943 978(2) angstrom. (C) 2016 Elsevier B.V. All rights reserved.