He was a Wales under-20 international, captaining the side at the 2012 and 2013 Junior World Cup where Wales finished as runners up. Jenkins captained team consisting of a number of future Wales senior internationals: in the 2012 championship he captained the side which became the first side from any country to defeat New Zealand at that level. His team-mates that day included future senior Wales regulars Rob Evans and Samson Lee as well as several other players who would go on to earn senior Wales caps including Tom Prydie, Dan Baker, Eli Walker and Matthew Morgan, as well as future Scotland international Luke Hamilton. In 2013, Jenkins would captain the side which finished runners-up, Wales' best performance at U20 level to date.