Electronic transitions of the linear MgC4H and MgC6H radicals have been observed in the gas phase using laser-induced fluorescence spectroscopy. The species were prepared in a supersonic expansion by ablation of a magnesium rod in the presence of acetylene, diacetylene, or methane gas. The transitions were recorded in the 445-446 nm region and assigned to the A (2)Pi-X-2 Sigma(+) systems (T-0 = 22 431.978(7) and 22 090.08(7) cm(-1)) based on previously reported mass-selective resonance-enhanced ionization spectra and the rotational structure. A spectral fit in MgC4H yields the rotational constants B '' = 0.04619(19) cm(-1) for the X (2)Sigma(+) state and B' = 0.04748(20) cm(-1) for A (2)Pi. Astrophysical implications are briefly addressed.