The purpose of this study was to verify the effectiveness of the Heads Up Tackling program for defensive players and its influence on safety and performance. Head impacts in football players are directly associated with brain and spine injury, and have been proposed to be associated with injuries such as chronic traumatic encephalopathy (CTE). Therefore, improvement of safety has been a challenge in American football, from the perspective of injury prevention. In 2012, USA Football, the national governing body for amateur American football in the USA developed the Heads Up Football (HUF) program which included “Heads Up Tackling” (HUT), a set of new guidelines for tackling. HUT has been attracting attention in the context of safe tackling through a new coaching methodology. Although in Japan so far, there have been no reports of football-related chronic injuries caused by head impacts, many concussions occur in football games. Therefore, it seem necessary to identify a methodology for teaching tackling techniques in order to reduce the risks of head and neck injury. A number of studies have focused on coaching intervention in relation to safety, and for reducing head impact exposure and injury. However, no reports have focused on the impact of these efforts on athletic performance during a game. If it could be confirmed that HUT reduces the risk of injury in football games without decreasing athlete performances, it would be a useful resource for instruction on tackling skills. Here, 4 matches in the Japan top league (X-league) 2014 and 2015 season were analyzed, before and after HUT intervention was executed in the preseason of 2015. A total of 166 coded tackles were compared in terms of “tackling characteristics”, “amount of injuries”, “effectiveness of tackling”, and “loss of yards” to examine the effect of HUT techniques on “safety” and “effectiveness”. The results revealed that (1) the frequency of “head down” tackling was significantly lower after HUT intervention, (2) the “amount of injuries” was reduced after HUT intervention, (3) there was no effect on the “effectiveness of tackling” in games, (4) “loss of yards” was reduced after HUT intervention, and (5) HUT appeared to reduce the risks of injury in football games, without decreasing tackling performance.