This work presents a green, simple, validated colorimetric method for the determination of tigecycline in lyophilized powder and laboratory prepared pharmaceutical wastewater. The suggested method depends on the reaction of tigecycline with Eosin-Y targeting its tertiary amino group, forming a reddish-orange ion pair complex with a wavelength of maximum absorbance of 555 nm. The greenness of this method was assessed by four methods; 1-National Environmental Methods Index assessment (NEMI), 2-Analytical Eco-Scale assessment, 3-Green Analytical Procedure Index assessment (GAPI), and 4-The Analytical Greenness Metric assessment (AGREE). They showed the significant greenness of the proposed method. The analyte followed a linear pattern over the concentration range of 1.0-14.0 μg/mL, with a lower detection limit of 0.21 μg/mL and a quantitation limit of 0.64 μg/mL. The suggested method was completely validated according to the International Conference on Harmonization (ICH) guidelines regarding linearity, accuracy, precision, specificity, and robustness, which permits its application for the intended purpose.