The clinical applications of stereotactic body radiotherapy or stereotactic ablative radiotherapy (SABR) for the treatment of primary and metastatic tumours of different organ sites have been expanding rapidly in the recent decade. SABR requires advanced technology in radiotherapy planning and image guidance to deliver a highly conformal ablative dose precisely to targets (or tumours) in the body. Although this treatment modality has shown promising results with regard to tumour control, some serious complications have been observed and reported. In order to achieve a favourable therapeutic ratio, strategies to mitigate the risk of complications must be in place. This overview will summarise the reported serious complications caused by SABR and strategies to mitigate the risk will be discussed.