Kammala wannan jumla: A lokacin yakin Mexico da Amurka, Granger ya yi yaƙi a cikin sojojin Winfield Scott. Ya shiga cikin Siege na Veracruz, yakin Cerro Gordo, yakin Contreras, da
Yaƙin Churubusco, da Yaƙin Mexico City. Granger ya karbi lambobi biyu don ƙarfin hali kuma a watan Mayu 1847 ya karbi kwamishinansa na yau da kullum a matsayin mataimakin mataimakin. Bayan yakin, ya yi aiki a kan iyakar yammacin Oregon sannan Texas. A shekara ta 1853 ya zama na farko laftanan.