When Emperor Napoleon ordered Masséna to take command of the Army of Portugal, Pelet went with him as his first "aide-de-camp". Though Pelet was a relatively low-ranking officer, the marshal relied heavily on his advice during the unsuccessful 1810–1811 invasion of Portugal. Pelet fought in the French invasion of Russia, including during Marshal Michel Ney's epic retreat at Krasnoi where he was wounded again. Promoted to general officer, he led troops in the 1813 and 1814 campaigns, including a brief stint as acting division commander. He led a regiment of the Old Guard at Waterloo.