Most often, reactive and disperse dyes are utilized separately in two- bath two-step dyeing method to dye polyester-cotton blend fabric. The cost of this conventional dyeing method is very expensive; energy and chemical usage is also quite higher in addition to this, the dyeing cycle is complex as compared to one-bath two-step dyeing methods or single-bath single-step dyeing methods. The single-bath single-step dyeing procedure with a single type of dye class was studied in this research. Following surface treatment of cotton through esterification procedures, polyester-cotton blend fabric dyed in single-bath single-step dyeing processes with disperse dye was examined. The association between time and the percentage of esterification was investigated at room temperature. Varying dye concentrations and dyeing temperatures were utilized to dye surface-treated p/c blend fabric in an HTHP dyeing machine. The color strength of dyed material and their fastness properties and the Surface chemistry by using FTIR were evaluated. The influence of dye concentration and temperature on color strength was investigated. With a 15% esterifying agent concentration and a reaction period of 2.5 h, the optimum value for surface modification was obtained, yielding a percent esterification of 34.95. The optimal value was attained with a dye concentration above 1% at a temperature of 120 °C, according to the dyeing experiment results. The findings of this study revealed that when compared to conventional two-bath dyed fabric, one-step one-bath dyed modified polyester/cotton blend with Disperse dye fabric has good wash fastness, and color strength, and is environmentally friendly.