The relationship between periodontology and orthodontics consists of a highly complex, bidirectional and close interaction that is now a days characterized by controversial scientific opinions and clinical approaches. Biologic basis of the orthodontic tooth movement is the selective resorption and formation of alveolar bone around the tooth in response to application of pressure to the tooth for a prolonged period. These tooth movements are specifically related to interactions of the teeth with their supportive periodontal tissues; therefore, orthodontic tooth movement is basically periodontal ligament phenomenon. It appears that every orthodontic intervention has some kind of periodontal dimension. Therefore, to enable coordinated perio-ortho therapy, both the specialists should be involved in establishment of an appropriate diagnosis and treatment planning as well as for evaluation of the progress of treatment undertaken. In this review article, a harmonious and mutually beneficial relationship shared between these two specialities will be highlighted.