He was instrumental in their 22–17 defeat of the Springboks in a Friendly match on 6 November 2009. Due to injury to squadmate Harry Ellis, he was able to hold down a starting place in the 2009–10 season. In February 2010, Youngs signed a new contract. His team-mates voted him Leicester Tigers Player of the Season for 2009/10. In a season littered with awards, he also picked up the Landrover Discovery of the Season award. He crowned off the season by playing in the 2009-10 Guinness Premiership final victory over Saracens.
He was picked for the revised England Saxons Squad on 13 January 2010, and upgraded to the revised Senior Squad as injury cover for Harry Ellis on 25 January 2010. Later that month, he made his debut for the England Saxons, against Ireland A. He made his senior England debut as a substitute on the wing for the injured Ugo Monye in the Calcutta Cup match against Scotland on 13 March 2010, and was an unused replacement in the match against France. He continued as part of the senior squad on their tour of Australia, and played in both Test matches.
Youngs made his first international start in England's 21 – 20 win over Australia in Sydney, on 19 June 2010. He played an important role in improving the England gameplan in the game, and scored a solo try in the first half. On 13 November 2010, Youngs was awarded man of the match award for his outstanding performance against Australia.