A haloalkalophilic Staphylococcus sp. SG‐13 produced an alkalistable xylanase in wheat bran medium. A 12‐fold purification was achieved by using standard purification techniques. The purified xylanase exhibited a dual pH optima of 7.5 and 9.2. The optimum temperature for enzyme activity was 50 °C. The enzyme was stable at 50 °C for more than 4 h. The xylanase exhibited K_m and V_max values of 4 mg ml⁻¹, 90 μmol min⁻¹ per mg for birchwood xylan and 7 mg ml⁻¹, 55 μmol min⁻¹ per mg for oatspelt xylan, respectively. The substrate binding affinity of xylanase was more for oatspelt xylan but birchwood xylan was hydrolysed more rapidly. The xylanase activity was stimulated by Fe²⁺, Ni²⁺, Cu²⁺ and dithiothreitol up to 60% and was strongly inhibited in the presence of Co²⁺, Hg²⁺, Pb²⁺, phenyl methane sulphonyl fluoride, ethylenediaminetetraacetic acid, and acetic anhydride up to 100%. The xylanase dose of 1.8 U g⁻¹ moisture free pulp, exhibited bleach boosting of kraft pulps optimally at pH 9.5–10.0 and 50 °C after 4 h of reaction time. Pretreatment of pulp with xylanase and its subsequent treatment with 8% hypochlorite, reduced the kappa number by 30%, enhanced the brightness and viscosity by 11% and 1.8%, respectively, and improved the paper properties such as tensile strength and burst factor up to 10% and 17%, respectively.