The respiratory tract infections have a growing concern by healthcare specialists. Carbocisteine, guaifenesin, and oxomemazine are widely used as co-formulated anti-cough drugs. For the first time, a precise, accurate, and green HPLC method has been developed and validated for their determination in their combined dosage forms. The separation was accomplished using a photodiode array detector at 220 nm with an isocratic green mobile phase consisting of phosphate buffer 0.025 M, (pH 3) and ethanol (75:25, v/v) at a flow rate of 1.0 mL/min and ambient temperature. The developed method was validated in accordance with ICH guidelines. Carbocisteine, guaifenesin, and oxomemazine were separated in less than 12 min at 1.569 ± 0.005 min, 8.546 ± 0.007 min, and 10.877 ± 0.008 min, respectively. The linear ranges for carbocisteine, guaifenesin, and oxomemazine were 31.25–187.50, 25–150, and 0.5–3.0 µg/mL, respectively. The developed method can be used in quality control laboratories for the simultaneous determination of the investigated drugs in their pharmaceutical dosage forms. In addition, it proved its superiority over the reported methods in terms of greenness using different assessment tools.