Spectroscopic constants of the first excited state (A) over tilde (2)Pi of MgNC have been predicted from three-dimensional potential energy surfaces determined by ab initio molecular orbital calculations at the multi-reference singles and doubles configuration interaction level. The equilibrium structure of (A) over tilde (2)Pi MgNC is linear with r(e)(Mg-N) of 1.8843 Angstrom and r(e)(N-C) of 1.1812 Angstrom. The predicted spectroscopic constants are as follows: the rotational constant B-0=6127 MHz, omega (1)=2101 cm(-1), omega (2)=163 cm(-1), omega (3)=586 cm(-1), and the spin-orbit coupling constant A(SO)=34.9 cm(-1). The Renner parameter epsilon was calculated to be 0.259 from the lower 1(2)A' and the upper 2(2)A' potential energy surfaces. Based on the thus predicted spectroscopic constants and epsilon, the observed laser-induced fluorescence spectra have been reinterpreted purely from the theoretical point of view within errors of a few wavenumbers. Present assignments indicate that only lines for kappa states have been observed.