A series of disperse dyestuffs derived from polyamidoamine dendrimer and thiazol derivatives were synthesized. The dyestuffs and corresponding intermediates were characterized by DSC, TLC, FTIR, 1H NMR, 13C NMR, UV–VIS and Elemental Analysis. Spectrophotometric investigations of the prepared dyestuffs in various organic solvents of different polarity were examined in order to obtain their absorption maxima and solvatochromism effects. The dyestuffs displayed λmax of between 336.4 and 427.8 nm and the molar extinction coefficient (εmax) of the dyestuffs varied from 4500 to 49,000 l mol−1 cm−1. The dyestuffs were finally applied for dyeing of polyethylene terephthalate fabrics in order to investigate their dyeing properties and the obtainable colour gamut. The results indicated that the presence of polyamioamine dendrimer as a core at the chemical structure of dyestuffs provided high build up properties under high temperature conditions. Most of the prepared dyestuffs displayed moderate light fastness and very good wash and dry heat fastness.