The vibrational spectrum of ground state nickel-monoethylene isolated at low temperature in solid argon has been reinvestigated. NiC2H4 and its various isotopic forms NiC2D4, (NiC2H4)-C-13, and NiCH2CD2, have been synthetized by direct Ni vapor and ethylene co-condensation in the rare gas matrices. Nine to ten fundamentals are observed for each species, and additional data can be derived from the observation of four combination bands. A normal coordinate analysis has been carried out at the harmonic level, based on the experimental isotopic frequencies, and C-C, Ni-C, and C-H bond force constants can be estimated at 5.61, 1.91, and 4.68 mdyn Angstrom(-1), respectively. These results are compared to the most recent theoretical prediction by Papal et al.