The heteronuclear LaMn(dhbaen)(OH)(NO3)(H2O)(4) complex was synthesized and perovskite-type hexagonal LaMnO3 was obtained by its thermal decomposition at approximately 700 degreesC, The complex and its decomposition products were analyzed using simultaneous thermogravimetric and differential thermal analysis (TG/DTA), X-ray diffraction (XRD) analysis, Fourier-transform infrared (FTIR) spectroscopy, Auger electron spectroscopy (AES), transmission electron microscopy (TEM) characterization, and specific surface area measurements. Although XRD analysis did not show the peaks of LaMnO3 for the sample sintered at 600 degreesC, the presence of polycrystalline LaMnO3 together with an amorphous phase was confirmed by TEM-selected area diffraction, Particle sizes of the samples decomposed at 600 degrees and 700 degreesC were 20 and 50 nm, respectively, For the conventional solid-state reaction method, XRD results showed the formation of a LaMnO3 single phase for the samples fired above 1000 degreesC, However, AES showed that the elemental distributions of La, Mn, and O on the surface were not homogeneous even for the sample sintered at 1200 degreesC. The thermal decomposition of the heteronuclear complex at low temperatures allows the synthesis of single-phase hexagonal LaMnO3 powders having nanosized particles, homogeneous and free of intragranular pores, which are suitable for electroceramics applications.