Tigecycline (TGC) is a novel potent antibiotic with recently proven anticancer activity against leukemia, glioma, and lung cancer. In-line TGC potentiometric sensors are fabricated for monitoring TGC in its pure form, pharmaceutical formulation, presence of its degradation products, and spiked plasma. In-line sensors act as greener, portable, and economical alternatives to the classical off-line separation-based techniques. Classical and advanced liquid-contact (LC) and solid-contact (SC) sensors were fabricated, where the best performance was observed with the modified SC sensor (sensor VI) with potassium tetrakis (4-chlorophenyl) borate as ionic exchanger, ꞵ-cyclodextrin ionophore and cobalt oxide nanoparticles, showing a Nernstian response of 30 mV decade−1 in the linear range of 10−2–10−6 M. Statistical comparison was carried out for the results obtained from proposed SC sensors and the official method on TGC pure form. Additionally, method greenness was evaluated using a semi-quantitative analytical eco-scale, scoring approximately 95 points, which was the highest greenness achievement score when compared to the proposed LC sensors or British pharmacopeial chromatographic method.