On 23 January 2017, Scannell was named in the Ireland squad for the opening two rounds of the 2017 Six Nations Championship. On 11 February 2017, Scannell made his debut for Ireland when, due to captain Rory Best's illness, he started against Italy in the Six Nations. Scannell 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, Scannell scored his first try for Ireland, doing so in the 55–19 win in the Red Bull Arena, New Jersey. When Scannell's brother Rory came on in the test as a replacement, they became the first Munster siblings to represent Ireland in the professional era. Having been called-up to replace captain Rory Best in Ireland's squad to tour Australia, Scannell went on to start in the second and third tests in Ireland's historic series victory.