<p>In this research, recycled polyester fabric was dyed using agro-sourced eco-friendly natural carrier called coumarin at dyeing process temperature of 100℃. The carrier modified glass transition temperature of recycled polyester fibers resulting in significant coloration process compared with synthetic carrier. Varying the dyeing process parameters such as carrier concentration, dye concentration, and low- and high-molecular-weight disperse dyes showed significant improvement yielding color with coumarin. The high concentration of the natural carrier resulted in significant penetration of the dye molecules proving a promising competitor of synthetic carrier. The overall color fastness properties with respect to rubbing, washing, light, perspiration were obtained from very good to excellent as well as prominent k/s value for the dyed fabric at 4&#xa0;g/l after carrier dyeing at 100℃. Coumarin does not pollute water and can replace the need for use of synthetic carrier providing environment friendly process for dyeing of recycled polyester fabric.</p> Graphical abstract <p></p>