He was named in José Luis Imhoff and Alex Wyllie’s squad for the 1999 Rugby World Cup squad, where the Pumas made the quarter-finals for the first time. Marcelo Loffreda took charge of the national side in 2000 and Contepomi retained his place, eventually nailing down a starting berth 2001.

He notably notched a full house on his way to 25 points in the 30–16 victory over Wales in Cardiff on 10 November 2001. He was also part of the 2003 Rugby World Cup squad, featuring in three of the Pumas’ pool games as they were forced to play four games in a fortnight.

Born 20 August 1977 in Buenos Aires, Contepomi started playing rugby for his secondary school Colegio Cardenal Newman, and then for Club Newman in Buenos Aires. In 2003 he joined Leinster from Bristol on a four-year contract following Bristol’s relegation in the 2002–03 Zurich Premiership.

In 2004, Contepomi weighed in with 14 points as Argentina condemned France to their first defeat at the Stade Vélodrome in Marseille. He also faced the British & Irish Lions in 2005 and at the end of 2006 he was part of the Pumas side that scored their first ever victory over England at Twickenham.

On 31 May 2007, the Royal College of Surgeons in Ireland in Dublin conferred him with the medical degrees of MB BCh BAO (NUI) LRCP&SI. He subsequently worked in Beaumont Hospital, Dublin.

Contepomi was one of the stars of world rugby and was also set to lead the Argentina national team into a new era after being named captain in 2008. The former U19, U21 and Sevens international made his Pumas debut against Chile in 1998 and has been an integral part of Argentinean rugby ever since.

Following the retirement of veteran scrum-half Agustín Pichot, Contepomi was handed the captaincy of the Pumas in 2008 by new coach Santiago Phelan ahead of the opening clash of the year against Scotland.

On 12 March 2009, it was announced that Contepomi would be leaving Leinster at the end of the season, and that he had signed a 4-year deal to join French side RC Toulon from the 2009–10 Top 14 season.

Contepomi played a role in the Leinster win over Munster in the Heineken Cup semi-final on 2 May 2009. After scoring a drop goal after 15 minutes in, he was helped off the pitch after suffering a knee injury half an hour in. An MRI scan confirmed he tore his anterior cruciate ligament and was expected to be out of action for 6 months post-op. Almost exactly on schedule, he made his Toulon debut on 21 November against Brive, coming off the bench and scoring a penalty in Toulon’s 19–10 win.

A knee injury suffered in Leinster’s Heineken Cup semi-final victory over Munster in 2009 ruled him out of action for over a year but he returned to Pumas colours in 2010 and won a 31-point haul in their 41–13 victory over Six Nations champions France.

Contepomi joined Argentina XV in 2015 as a head coach alongside Ricardo Le Fort. In 2018, he was appointed as new Backs Coach to Leinster, succeeding Girvan Dempsey, who moved to Bath.