Cyanoacetylene (HC₃N) was detected in 1971 in Sgr B2 by Barry Turner. Confirming observations include the detection of a second rotational line by Dickinson in 1972, a third line by McGee et al. in 1977, and detections of two of the ¹³C isotopomers by Gardner & Winnewisser in 1975. The first extragalatic detection was reported in 1990 by Mauersberger et al. toward the Silver Dollar galaxy. In was also observed in comet Hale-Bopp by Bockelée-Movan et al. and also in Titan's atmosphere by Kunde et al., making it one of the most diversely observed astromolecules to date.

UPDATE (July 2018): Cyanoacetylene was detected in the protoplanetary disk MWC 480 by Chapillion et al. in 2012.

Cyanoacetylene is the prototype of one of the most extensive family of known interstellar species, the cyanopolyynes, which consist of H-(CC)_n-CN for n greater than 1.