While playing for Newport, Jenkins faced the three major Southern Hemisphere teams, Australia, South Africa and New Zealand.

Jenkins made his début for Wales against Scotland at the Cardiff Arms Park on 5 February 1910 as part of the Five Nations Championship.

It was a one-sided affair with Wales scoring 4 tries without reply, including one from fellow new cap Billy Spiller.

His first game for the Hornets took place on 17 September 1910, and on 10 December he was selected for his first rugby league international when he was chosen to represent Wales against England at Coventry.

Ernie Jenkins played as a forward in Rochdale Hornets' 12–5 victory over Oldham in the 1911–12 Lancashire Cup Final during the 1911–12 season at Wheater's Field, Broughton, Salford on Saturday 2 December 1911, in front of a crowd of 20,000.