Rubuta ci gaba ga wannan sakin layi - 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, yakin Churubusco
, da kuma yakin 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.