MicroRNA 155 (miR-155) is a key proinflammatory regulator in clinical and experimental rheumatoid arthritis (RA). Here we generated a miR-155 genome knockout (GKO) RAW264.7 macrophage cell line using the clustered regulatory interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (CAS9) technology. While upregulating the Src homology-2 domain-containing inositol 5-phosphatase 1 (SHIP1), the miR-155 GKO line is severely impaired in producing proinflammatory cytokines but slightly increased in osteoclastogenesis upon treatment with receptor activator of nuclear factor-κB ligand (RANKL). Taken together, our results suggest that genome editing of miR-155 holds the potential as a therapeutic strategy in RA.