Despite not making his first-team debut for St Helens until 2017, he was first picked to play for the Welsh international side in October 2015 when he came on as an interchange player in Wales' 14–6 victory over France.

[6] His first Super League appearance came on Good Friday, 14 April, 2017 in the derby match against Wigan where he scored a try on debut.

[10] During the 2021 Challenge Cup Grace was the leading try-scorer, scoring seven including a hat-trick against Huddersfield in the quarter-finals, and two in the semi-final against Hull FC.

[17] On 2 August 2022, it was announced that Grace had ruptured his achilles during St Helens heavy defeat against Salford which would rule him out for the remainder of the 2022 Super League season.

[21] Grace signed a short-term contract with Bath on 16 February 2024, and made his debut on 9 March 2024, in a friendly against Gloucester.

[2] He was called up to the Wales national rugby union team for the first time on 20 June, after Keelan Giles was ruled out of the summer tour of Australia, playing in the uncapped match against Queensland Reds, scoring a try on debut.