On 23 January 2017, Earls was named in the Ireland squad for the opening two rounds of the 2017 Six Nations Championship. In Ireland's opening fixture of the tournament against Scotland on 4 February, Earls scored a try, though Ireland lost 27–22. On 11 February, Earls scored two tries in Ireland's 63–10 win in the Stadio Olimpico against Italy. He also started against France, Wales and England. He was also selected in the squad for the 2017 Summer Tour against the United States and Japan. On 10 June 2017, in the one-off test against the United States, Earls scored two tries, made three assists and won the Man-of-the-Match award in Ireland's 55–19 win in the Red Bull Arena, New Jersey. On 17 June 2017, Earls again scored two tries, this time in Ireland's 50–22 win against Japan in Shizuoka Stadium, Shizuoka. His tally of nine tries in an international season set a new record for Ireland. He also started the second test against Japan, which Ireland won 35–13 to seal the series victory.