Osteoarthritis (OA), the most common form of arthritis, is characterized by pain and cartilage damage; it usually exhibits gradual development. However, the pathogenesis of OA remains unclear. This study was undertaken to improve the understanding and treatment of OA. OA was induced in 7-week-old Wistar rats by intra-articular injection of monosodium iodoacetate (MIA); subsequently, the rats underwent oral administration ofBifidobacterium longumBORI (B. BORI). The effects ofB. BORI were examined in chondrocytes and an MIA-induced OA rat model. In the rats,B. BORI-mediated effects on pain severity, cartilage destruction, and inflammation were recorded. Additional effects on mRNA and cytokine secretion were analyzed by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. Paw withdrawal threshold, paw withdrawal latency, and weight-bearing assessments revealed that pain severity in MIA-induced OA rats was decreased afterB. BORI treatment. Histopathology analyses and three-dimensional surface renderings of rat femurs from micro-computed tomography images revealed cartilage protection and cartilage loss inhibition effects inB. BORI-treated OA rats. Immunohistochemical analyses of inflammatory cytokines and catabolic markers (e.g., matrix metalloproteinases) showed that the expression levels of both were reduced in tissue fromB. BORI-treated OA rats. Furthermore,B. BORI treatment decreased the expression levels of the inflammatory cytokine monocyte chemoattractant protein-1 and inflammatory gene factors (e.g., inflammatory cell death markers) in chondrocytes. The findings indicate that oral administration ofB. BORI has therapeutic potential in terms of reducing pain, progression, and inflammation in OA.