In 2015, he was included in the South Africa Under-20 squad that toured Argentina. He started both of their tour matches and was then included in the final squad for the 2015 World Rugby Under 20 Championship. He started all three of their matches in Pool B of the competition; a 33–5 win against hosts Italy, a 40–8 win against Samoa which saw Du Toit score South Africa's first try of the match in the seventh minute and a 46–13 win over Australia to help South Africa finish top of Pool B to qualify for the semi-finals with the best record pool stage of all the teams in the competition. Du Toit started their semi-final match against England, but could not prevent them losing 20–28 to be eliminated from the competition by England for the second year in succession. He started their third-place play-off match against France, scoring his second try of the tournament to help South Africa to a 31–18 win to secure third place in the competition.