During the War of the Fourth Coalition in 1806, Barrois led his regiment at the battles of Halle, Nossentin and Lübeck. In 1807, he fought at the Battle of Mohrungen. On 14 February 1807 he was promoted to general of brigade. Given a brigade in Dupont's division, Barrois led his troops in a skirmish at Braniewo (Braunsberg) and at the Battle of Friedland on 14 June 1807. At Friedland, Dupont's division greatly distinguished itself, piercing the Russian center and repelling attacks by the Russian Imperial Guard. In recognition, Napoleon appointed Barrois a Grand Officer of the Legion of Honor.