A series of oligomeric acid azo dyes has been prepared by coupling various aromatic diazonium salts to 1,5-dihydroxy-naphthalene formaldehyde (1,5-DHNF) oligomer. They were evaluated in terms of their softning point, yield, colour, solubility, IR and UV-Vis spectra. Structure property relationships are discussed and dyeing on wool, silk and nylon-6,6 were assessed. Dyeing on wool, silk and nylon-6,6 resulted in yellow, orange and brown to red colorations having excellent light fastness and washing fastness.