This work evaluated the impact of brownstock pulp kappa number variations on modified pulping process, oxygen delignification, bleaching, and the physical characteristics on bleached pulp. Wood chips of 6-year-old Eucalyptus grandis x Eucalyptus urophylla from Brazil were used. A modified pulping process was performed with the purpose of achieving two delignification levels on brownstock pulp: kappa 18 and kappa 15. Pulps were submitted to oxygen delignification and elemental chlorine-free (ECF) bleaching to achieve 89.5 ± 0.5% of ISO brightness. Subsequently, pulps were refined in four levels (0, 750, 1500, and 3000 rotations) for physical mechanical tests. Delignification increased after increasing the cooking H factor and alkali charge. As a result, delignification negatively impacted the pulping yields (from 56.1% to 55.0%) and the pulp viscosity (from 1,317 cm³/g to 1,227 cm³/g). Pulps with an initial kappa of 15 presented more efficient oxygen delignification and lower consumption of bleaching reagents. The final viscosity of these pulps were lower (899 cm³/g against 963 cm³/g), however, than that of the pulps with an initial kappa of 18. Furthermore, the pulps with a higher unbleached kappa demanded less refining energy and had lower capillarity. The other physical properties were not influenced by the brownstock delignification level.