Organic-inorganic lead iodide perovskites are efficient materials for photovoltaics and light-emitting diodes. We report carrier decay dynamics of nanorods of mixed cation formamidinium and methylammonium lead iodide perovskites [HC(NH)][CHNH]PbI (FAMAPbI) synthesized through a simple solution method. The structure and FA/MA composition ratio of the single-crystal FAMAPbI nanorods are fully characterized, which shows that the mixed cation FAMAPbI nanorods are stabilized in the perovskite structure. The photoluminescence (PL) emission from FAMAPbI nanorods continuously shifts from 821 to 782 nm as the MA ratio (x) increases from 0 to 1 and is shown to be inhomogeneously broadened. Time-resolved PL from individual FAMAPbI nanorods demonstrates that lifetimes of mixed cation FAMAPbI nanorods are longer than those of the pure FAPbI or MAPbI nanorods, and the FAMAPbI displays the longest average PL lifetime of about 2 μs. These results suggest that mixed cation FAMAPbI perovskites are promising for high-efficiency photovoltaics and other optoelectronic applications.