Possibilities and limitations in using transmission electron microscopy to characterize pure NaAlH4 and transition metal enhanced NaAlH4 have been investigated in detail. NaAlH4 is extremely sensitive to O2 and H2O and must be handled under inert atmosphere at all times. Furthermore, it is highly unstable under the electron beam and only basic techniques such as diffraction contrast imaging and selected area diffraction that can be performed with a low flux electron beam can be used without the NaAlH4 decomposing. By comparison, phases containing transition metal additive are very stable under the electron beam. The latter are investigated by a combination of high resolution imaging, electron diffraction and spectroscopy to determine distribution, composition, crystal structure and defect content in ball milled and hydrogen cycled, TiCl3 and FeCl3 enhanced NaAlH4. It is demonstrated that a large amount of the added Ti or Fe is located at the surface of the NaAlH4 grains as a combination of crystalline and amorphous Al1-xTMx (TM = Ti, Fe) nanoparticles.