Ankylosis of the temporomandibular joint (TMJ) can be a result of trauma, degenerative changes and infection or of a space-occupying lesion and, when occurring during early childhood, can result in severe functional disability and facial distortion. Septic arthritis of the TMJ is extremely rare in young infants. We report two children with TMJ ankylosis that is believed to have been a consequence of undiagnosed septic arthritis of the TMJ in the neonatal period.