Montiel made his senior international debut for Argentina in 2019. He was a part of the squads that won the Copa América in 2021 and 2024 and the FIFA World Cup in 2022, scoring the winning penalty in the shoot-out of the latter final.
Montiel played four league matches the 2016–17 season. On 30 October, he was sent off in a 2–2 draw at Arsenal de Sarandí.[5] He lifted the Copa Argentina trophy after playing all the matches from the last 16 to the final, in which his team beat Atlético Tucumán.[6] He played in the 2017 Copa Libertadores, scoring a goal and assisting three, playing every minute from the quarter-finals to the semi-finals, where River Plate were defeated by Club Atlético Lanús; his first career goal came on 1 November in a 4–2 loss at Lanús.[7]
In the 2017–18 season, Montiel played 35 matches, fifteen of them coming in the league. He made 14 appearances he made as the team lifted the Copa Libertadores at the Santiago Bernabéu Stadium against Superclásico rivals Boca Juniors.[8] Playing five matches in the Copa Argentina, the team were eliminated on penalties in the semi-finals against Club de Gimnasia y Esgrima La Plata. The team secured a double that season as they beat Boca in the Supercopa Argentina.
The following season, Montiel played 12 matches in the league without being substituted. For the second season in a row, Montiel reached the Copa Libertadores final after twelve matches; however, River Plate would be defeated by CR Flamengo. He won the Copa Argentina once more as River beat Central Córdoba - he played every minute in the cup run. After winning last season's Copa Libertadores, River contested the FIFA Club World Cup where they finished third. An injury prevented him from playing in the Super Cup. After recovering, he returned to contest the Recopa as River overcame a 1–0 first-leg defeat to win the trophy with a 3–0 win against Club Athletico Paranaense.[9]
On 20 February 2021, Montiel scored his first league goal for River, a penalty in a 3–0 win against Rosario Central in the first game at the Estadio Monumental after a six-month renovation.[10]
Montiel was sent off on 6 November 2022 in a 1–1 Seville derby draw at Real Betis for a 38th-minute foul on Álex Moreno.[14] On 31 May 2023, he scored the winning penalty in the Europa League final against Roma in a 4–1 victory in the penalty shootouts after a 1–1 draw, which secured their seventh title in the competition.[15]
Loan to Nottingham Forest
On 23 August 2023, Montiel signed for Premier League club Nottingham Forest on a season-long loan with the option to make the move permanent. He became the third Argentine in history to sign with the club.[16][17]
Return to Sevilla
After one season in the Premier League, Montiel returned to Sevilla after completing his loan spell for Nottingham Forest after playing 802 minutes for the English team. Forest had shown interest in signing him permanently, as well as fellow English side Everton FC and the Dutch team Feyenoord, but ultimately Montiel returned to Spain.[18][19]
On 11 June 2021, Montiel was one of the 28-man squad announced by Argentina for the 2021 Copa América tournament.[22] He played four of the seven matches played by the team in the tournament including the final victory, which he had to complete with a bleeding ankle as a result of a tackle from Fred in the first half of the game.[23]
In November 2022, Montiel was named in the final squad for the 2022 FIFA World Cup in Qatar.[24] On 18 December, he conceded a penalty late in extra time after a handball which Kylian Mbappé scored, but Montiel then scored the tournament-winning penalty kick for Argentina in a 4–2 victory against France to win the final, when the game went to penalties after a 3–3 draw.[25]
In June 2024, Montiel was included in Lionel Scaloni's final 26-man Argentina squad for the 2024 Copa América.[26]
Personal life
In June 2023, Mundo Deportivo reported that Argentine police had charged Montiel with sexual abuse in relation to an alleged incident on 1 January 2019, despite Montiel denying the allegations.[27]