O21 will use Unit 6, its newest HD truck. The unit will operate as the presentation unit for ITV Sport, supported by Unit 3 which will produce the world feed.
The British Touring Car Championship season starts on 30 March on ITV4.
O21 managing director Ewen Hamilton, said "We are delighted to extend our relationship for a further three years and are confident that our new units, equipped with the latest broadcast technology, will capture all of the excitement of this long standing ITV Sport tournament."
ITV's director of news and sport, Mark Sharman, said: “The British Touring Car Championship is a significant undertaking for ITV Sport and I'm very pleased that we can rely on the expertise and resources of O21 Television as we expand our coverage of the event on ITV4.”
021 Television is based in Birmingham.