Nano-sized lanthanum manganites (LaMnO₃) were prepared by spray pyrolysis process from the spray solution with citric acid as organic additive. The LaMnO₃ precursor powders obtained from the spray solution with citric acid had thin wall and hollow structures. The thickness of the wall of the precursor powders was below 50 nm. The post-treated LaMnO₃ powders had slightly aggregated morphology of the primary powders with nanometer size. The post-treated LaMnO₃ turned to nano-sized powders after simple milling by hand using agate mortar. The mean sizes of the LaMnO₃ powders obtained from the spray solutions with concentrations of citric acid as 0.4 and 0.8 M at a post-treatment temperature of 800°C were 80 and 200 nm, respectively. The mean size of the LaMnO₃ powders changed from several tens nanometer to submicron size according to the post-treatment temperatures. The mean crystallite sizes of the LaMnO₃ powders obtained from the spray solution with citric acid at post-treatment temperatures between 700 and 1000°C changed from 26 to 36 nm.