This study examine the injuries suffered by players (n=166) of the Spanish national men’s under-18 and under-20 rugby teams between 2015 and 2017, and identifies the actions involved in their appearance. All injuries (total n=78) sustained during matches and training were recorded as recommended by World Rugby, and injury incidence rates per 1000 player-hours (ph) calculated for both types of activity. Injuries occurred more commonly during matches than during training (incidence 105.3 [95%CI 78.7-131.9] per 1000 [ph] of match play, vs. 1.16 [95%CI0.69-1.62] per 1000 ph of training), and most days absent per 1000 ph during matches with <3 days rest since the previous match (4209.2 [95%CI 3516.2-4902.1] per 1000 ph of match play, vs. 1947.4 [95%CI 1511.8-2382.9] per 1000 ph of match play in matches with >3 days rest). These results provide information that may be useful in the development of strategies aimed at reducing the incidence of injuries.