Despite only being promoted to the Catalans first-team squad in 2010, he played for the French national side at international level; coming off the bench against England in June 2009.

[3] He represented France in the 2010 European Cup and was named in the French squad for the 2013 Rugby League World Cup, he managed to kick the winning field goal against the Mal Meninga coached Papua New Guinea national side 9–8.

On 14 August 2014, Championship side London Broncos announced the signing of Barthau on a 2-year deal until the end of 2016.

[5][6] He was named in the France 23 man squad for the 2014 European Championship against Wales, Ireland and Scotland.

Barthau played in France's lone international fixture of 2016, an end of year test match against England in Avignon.