The role of MR imaging in pediatric arthritis is to detect early manifestations of arthritis, evaluate the extent of disease, and monitor disease activity during treatment. More specifically, MR imaging can characterize the pediatric arthropathy based on typical imaging findings, detect early signs of synovitis and erosions, stage the severity of joint involvement, demonstrate associated internal derangement, monitor disease progression or treatment response, and evaluate for complications. This article discusses MR imaging findings of juvenile idiopathic arthritis, enthesis-related arthritis, juvenile psoriatic arthritis, and articular findings in collagen vascular diseases, septic arthritic, hemophilia, neuroarthropathy, and pseudoarthridities.