Laser-ablated Ni atoms and electrons react with CO in excess argon during condensation to form the Ni(CO)(1-4) complexes and Ni(CO)(1-3)(-) anions. Matrix infrared spectra of the neutral complexes with (CO)-C-12-O-16, (CO)-C-13-O-16 and (CO)-C-12-O-18 substitution are in agreement with earlier reports with thermal Ni atoms. In addition, new absorptions at 1847.0, 1801.7, and 1858.8 cm(-1) exhibit isotopic spectra in excellent agreement with DFT calculations for the Ni(CO)(1-3)(-) anions. An experiment doped with the CCl4 electron-trapping molecule gave the same Ni(CO)(1-4) spectrum without the corresponding anions, which strongly supports this identification of the molecular anions.