On March 3, 1847, Cadwalader was appointed brigadier general and took command of a brigade of reinforcements being sent to Winfield Scott in central Mexico. His unit was designated the 2nd Brigade in the newly formed 3rd Division under Gideon Pillow. He participated in the battles of Contreras, Churubusco, and Chapultepec. For his services at Chapultepec, he was brevetted major general in the Regular Army, to rank from September 13, 1847.