The present work relates to the synthesis of iron and iron oxide based particles via Aerosol Spray Pyrolysis; a continuous and scalable aerosol synthesis method. Different process parameters included the temperature of reactor synthesis, flow rate/type of carrier gas and post treatment temperature as well as precursor solution chemistry, concentration, solvent and reactant type and such parameters are evaluated with respect to their effect on the synthesized particles crystallinity, morphology, iron oxidation state and mean particle diameter of produced powders. Three different iron precursor sources are employed: chloride, nitrate and a dispersible gel derived from a steel industry byproduct. Iron nitrate and chloride aqueous solutions were sprayed at four different concentrations in order to evaluate the effect of the nature of the iron precursor salt on the main attributes of the particle synthesized. Particle diameter was calculated theoretically based on models from the literature describing nucleation at the droplet level, while mean diameter of the synthesized particles was experimentally measured on line at the exit of the reactor. Ex situ TEM characterization provided the necessary morphological data to elaborate on the mechanisms of produced particles formation and explain observed deviations from the theoretically calculated mean particle diameter values.