Although epithelial NF-κB signaling is important for lung carcinogenesis, NF-κB inhibitors are ineffective for cancer treatment. To explain this paradox, we studied mice with genetic deletion of IKKβ in myeloid cells and found enhanced tumorigenesis in Kras^G12D and urethane models of lung cancer. Myeloid-specific inhibition of NF-κB augmented pro-IL-1β processing by cathepsin G in neutrophils, leading to increased IL-1β and enhanced epithelial cell proliferation. Combined treatment with bortezomib, a proteasome inhibitor that blocks NF-κB activation, and IL-1 receptor antagonist reduced tumor formation and growth in vivo. In lung cancer patients, plasma IL-1β levels correlated with poor prognosis, and IL-1β increased following bortezomib treatment. Together, our studies elucidate an important role for neutrophils and IL-1β in lung carcinogenesis and resistance to NF-κB inhibitors.