The present study was performed to ascertain the annual changes in the number and nature of traumatic head injuries that occur in high-school rugby matches, and as an exploratory investigation of approaches to improve safety in the future. It was based on injury reports submitted at the time of injury to the Kansai Rugby Football Union between Apr. 2009 and Mar. 2016. The finding was that the mean number of reported cases of traumatic head injury per year during the three pre-amendment years from Apr. 2009 to Mar. 2011 was 18.0, whereas that during the five post-amendment years from Apr. 2012 to Mar. 2016 was 36.2. Of all the traumatic head injuries, those with the highest numbers and proportions of cases for each of the four factors were as follows: (i) occasion of injury: during a match, 115 (48.9%); (ii) condition of the pitch: grass, 105 (44.7%); (iii) school grade: 2, 104 (44.3%); and (iv) cause of injury: tackling, 115 (48.9%). In addition, the odds ratios (ORs) for brain concussion at post-amendment as compared with pre-amendment and for occurrence on grass as compared with on soil were significant 2.83. An exploratory investigation was conducted to clarify whether different factors are associated with the severity of pre- and post-amendment injuries, but no significant ORs were found. In conclusion, the establishment of guidelines related to brain concussion in 2012 increased the number of reports of injuries due to high-school rugby and had a definite effect on prompt treatment of brain concussions.