For 20 years, antibacterial functionalization has been one of the most attractive research fields in the textile industry. Nowadays, globalization has spread the microorganisms everywhere and produced many epidemics and pandemics such as smallpox, cholera, tuberculosis, yellow fever, Spanish flu, and coronavirus. The textile materials treated with triclosan would be a strong alternative to obtain antibacterial function against microorganisms for the medical applications, such as face masks, lab coats, and wound dresses. This study aimed to investigate the characterization, antibacterial properties, and durability of triclosan on polyester, polyester/cotton, and cotton surfaces. The pure triclosan and presence of triclosan in solutions were detected by gas chromatography–mass spectrometry chromatograms. It can be seen that surfaces were homogeneously covered by triclosan on scanning electron microscope micrographs, and there were new bands on Fourier transform infrared spectra after treatments. Large inhibition zones around all surfaces were observed, and antibacterial activity slightly increased depending on increasing chemical concentrations. The samples demonstrated strong biocidal activity to bacteria for 3 h. They lost their antibacterial properties after washing, but they showed good antibacterial (bactericidal) properties and satisfactory durability to washes. The results show that triclosan is a highly effective and durable chemical on polyester and cotton surfaces for medical textile applications.