Highly (111)-oriented and conformal iridium (Ir) films were deposited by a liquid source metalorganic-chemical-vapor-deposition process on various substrates. An oxygen-assisted pyrolysis of (methylcyclopentadienyl) (1,5-cyclooctadiene) Ir precursor at a wide range of substrate temperatures (Tsub) between 300 and 700 °C was used. At a low Tsub of 350 °C, the randomly oriented polycrystalline films exhibited an I111/I200 x-ray intensity ratio of 6. However, the films deposited at Tsub = 700 °C on native SiO2 and amorphous SiO2 surfaces were highly oriented with the I111/I200 ratios of 277 and 186, respectively. The transmission electron microscopy study revealed continuous, dense, and faceted microstructures of Ir films. Also, the step coverage of Ir on TiN (64%) was higher than that on amorphous SiO2 (50%) surfaces.