[4] In January 2015, following Arthur's impressive performances at the Copa São Paulo de Futebol Júnior, he was promoted from Grêmio's youth team under first-team manager Luiz Felipe Scolari.

In 2016, Arthur made his league debut in the last match of the season, a 1–0 home loss against Botafogo, replacing Kaio in the second half.

In his Copa Libertadores debut, a 1–1 away draw against Club Guaraní, he was named man-of-the-match after completing 40 passes, with an impressive 100% success rate.

His playing style and build earned drawn comparisons with Spanish midfielders Andrés Iniesta and Thiago Alcântara,[5] and attracted interest from European clubs such as Chelsea,[6] Barcelona and Atlético Madrid.

In November, was elected by Conmebol the man of match in the second leg of the Copa Libertadores final against Lanús, despite playing only 50 minutes due to an injury.

[11] Arthur Melo made his competitive debut at the 2018 Supercopa de España on 12 August, in which Barcelona won 2–1 over Sevilla.

[20] He returned to Italy at the end of his loan spell having made just one substitute appearance totalling 13 minutes all season.

[25] On 15 September 2017, Arthur received his first senior call-up to the Brazil squad to face Bolivia and Chile for the 2018 FIFA World Cup qualification.

[30] Arthur scored his first senior international goal for Brazil on 17 November 2020, the opener in an eventual 2–0 away win over Uruguay in a 2022 FIFA World Cup qualifier.

His agility, technical ability, dribbling and movement – both on and off the ball – allow him to create space and control the flow of play in midfield, whilst his exceptional vision, playmaking ability, and precise passing allow him to retain possession, create chances, and make decisive passes for teammates.