Q. infectoria is found to exhibit a variety of pharmacological properties such as astringent, anti-diabetic, anesthetic, antiviral, antifungal [21], antibacterial [22], larvicidal [23], anti-inflammation [24] and wound-healing [25] properties. The literature shows that tannins, especially those of plant origin, have been found to possess antimicrobial activity [26]. The high tannin component present in oak galls might be responsible for its antimicrobial activity. The purpose of this research is to study the dyeing, fastness, and antimicrobial properties of woolen yarns using gallnut extract as a natural dye. The fastness properties of dyed samples were obtained with respect to light, washing, and rubbing. CIELab and K/ S values were also recorded. The antimicrobial activity of gallnut extract before and after application on woolen yarn was tested against a gram-negative bacterium (Escherichia coli), gram-positive bacterium (Staphylococcus aureus), and common fungus (Candida albicans). The durability of antimicrobial activity towards washing was also examined.