This paper presents a purification process of hydrogen bromide (HBr) gas by fractional distillation technique and its use for performance enhancement of copper–HBr laser (Cu–HBrL). The residual impurities in HBr were suppressed by a two-step distillation process at temperatures of and . The lowering of the impurities was confirmed by comparing the mass spectrograph of the HBr gas before and after distillation, using a quadrupole mass spectrometer. The effect of the purified HBr gas on the performance of Cu–HBrL average output power as well its electrical discharge characteristics were studied. More than 37% improvement in the laser average output power (40 to 55 W) was observed with the use of this distilled HBr gas compared to undistilled gas. The underlying mechanism of the enhancement was analyzed by comparing electrical discharge characteristics in the two cases. The improvement in Cu–HBrL performance with distilled HBr gas was attributed to lowering of bromine and hydrogen concentration, mainly manifested as increased average electrical energy coupling to the discharge. This resulted in increased laser gain as well as gain volume, which were reflected in increases in laser output power and beam diameter.