The present study analyzed the effects of cold treated brass wire electrode for the machining of hardened high-strength low-alloy (HSLA) steel on wire electric discharge machine. Cold treatment of brass wire at − 70 °C for 24 h has refined its microstructure which results in an increase in electrical conductivity by 24.5%. The experimental work is designed using fractional factorial design to determine the relationship of input variables including servo voltage (SV), pulse on time (T on), pulse off time (T off), wire type (W t), wire tension (T w), and flushing pressure (F p) and response measures including cutting speed (CS), surface roughness (Ra), and kerf width (Kf). In W t , two kinds of brass wires including cold treated (CT) and non-cold treated (NCT) have been used. Empirical models for cutting speed (CS), surface roughness (Ra), and kerf width (Kf) are developed, and their contribution is analyzed through the analysis of variance (ANOVA) technique. Desirability function offers the best combination of input variables to maximize CS and minimize both Ra and Kf simultaneously. T on is observed as the most effective input variable for all response measures, followed by W t and T off. CT brass wire has been observed as the best alternative in multi-objective optimization.