Selected in the Ireland under-20s squad for the 2019 Six Nations Under 20s Championship, Wycherley started the wins against England, Scotland, Italy, France, against whom Wycherley scored two tries and won the Man-of-the-Match award, and Wales, as Ireland secured their first grand slam in the tournament since 2007. He was retained in the under-20s squad for the 2019 World Rugby Under 20 Championship when it was confirmed in May 2019.