Sleightholme was named in the
England squad for the
2019 Six Nations Under 20s Championship, and he made his debut at that level in the opening game against
Ireland. He subsequently scored a try in England's final pool game against
Australia, with England eventually finishing the tournament in fifth place. Coach
Alan Dickens named Sleightholme in his England squad for the
2020 Six Nations Under 20s Championship and he made one appearance during the tournament against
Scotland. In September 2021 Sleightholme was called up to the senior England side for a training camp. He was included in the squad for their
2024 tour of New Zealand and on 6 July 2024 made his debut as a substitute in the opening Test defeat to the
All Blacks at
Forsyth Barr Stadium. In November 2024 Sleightholme scored his first tries at senior international level with a double in a loss against
Australia during the
2024 Autumn Nations Series. He also scored in their next game during a defeat against
South Africa. Sleightholme went on to score his fourth try in five games in their last Autumn international fixture of 2024, a 59–14 win against
Japan. This equalled the amount his father, Jon, had scored for England. In February 2025, he was called up to the senior training squad replacing
Cadan Murley for the
2025 Six Nations. He was subsequently named in the starting lineup to make his tournament debut in the second round against
France.
List of international tries . ==References==