Hydrogen isocyanide (HNC) was detected in 1972 via its J=1-0 rotational line at 90.7 GHz by Snyder & Buhl and Zuckerman et al. in W51 and NGC 2264, respectively. While Snyder & Buhl assigned the line to HNC, definitive experimental data to confirm the assigment was not available until the laboratory study of Blackman et al. was published in 1976. Subsequently, the three singly isotopically-subtituted forms were quickly found: HN¹³C by Brown et al. in 1976, DCN by Godfrey et al. in 1977, and H¹⁵NC by Brown et al. also in 1977. HNC was first detected in an extragalactic source, IC342, by Henkel et al. HNC has also been observed in a number of comets, beginning with the detection in Hyakutake by Irvine et al.

HNC is much less stable than its isomer, hydrogen cyanide (HCN). HNC is often far more abundant than it would be if interstellar clouds were in chemical equilibrium. But low temperatures and pressures mean than dark clouds take a very long time to reach equilibrium.

January 2021 - HNC has now been detected in the mid-IR by Nickerson et al. toward Orion IRc2 with SOFIA.