Constantin played four games for
Romania, making his international debut on 27 May 2004, when he came as a substitute and replaced
Mirel Rădoi in the 82nd minute of a friendly which ended with a 1–0 loss against
Ireland. In 2007 he played in a friendly against
Germany which ended with a 3–1 loss and in a
Euro 2008 qualification match against
Albania which ended with a 6–1 victory. Constantin's last appearance for the national team was on 12 August 2009 in a friendly which ended with a 1–0 victory against
Hungary. On 25 March 2008, he was decorated by the president of
Romania,
Traian Băsescu for the results on
Qualifying to EURO 2008 and qualification to
UEFA Euro 2008 Group C with Medalia "Meritul Sportiv" — (The Medal "The Sportive Merit") class III. ==Controversy==