In this research, novel high-molecular-weight cross-linked polyacrylate polymers have been synthesized by the inverse emulsion free radical polymerization technique. The optimal polymerization conditions were studied in terms of the initial polymerization temperature, total monomer concentration, thermal initiator type and amount, cross-linker type and amount, and co-monomer type and concentration. FTIR spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM) were used to characterize the prime polymer. Then, the optimally prepared polymer was incorporated into various pigment and dye paste formulations to be tested as a rheology modifier for textile printing pastes. The prepared modified pastes were applied for printing on cotton-polyester (35:65) fabric via the flat screen printing method. More interestingly, the synthesized polymer was compared with a commercially used product, ARGOPRINT 160 (ARGON Company, China). The color strength (K/S) values and color fastness of the printed fabrics to washing and rubbing were also investigated. The results showed that the prepared acrylate polymers revealed better efficiency as a thickening and modifying agent for improving the properties of printed fabrics (e.g., handling and color fastness against washing and rubbing), as compared with the commercially used one.