The rotationally resolved A(3)Sigma (-)(u)-X(3)Sigma (-)(g) electronic spectrum of the NC5N radical has been observed in the gas phase by cavity ring down spectroscopy in a supersonic plasma. The origin band is at nu (00) = 22832.7(1) cm(-1) and a rotational analysis gives constants B-0" = 0.02799(4) and B-0' = 0.02778(3) cm(-1). These are compared to the B-e values available from structures predicted by density functional theory and show that the molecule has a linear and centro-symmetric NCCCCCN structure.