Copper oxide thin films have been grown by successive ionic layer adsorption and reaction technique, which is inexpensive, environmentally friendly and simple onto soda-lime glass substrates from an aqueous copper (II) chloride dehydrate solution with and without the addition of ascorbic acid (AA) at 70 °C. Surface morphology, crystalline structure, chemical compositions, optical and electrical properties of thin films were investigated with a focus on the influences of different concentrations of AA. The analysis exhibited that the main physical performances of the CuO films were found to change with AA content. Estimated crystallite sizes decreased from 24.64 to 12.78 nm with the addition of AA in the growth bath solutions. The optical bandgap energy of CuO is found to increase from 1.42 to 1.55 eV as a consequence of the increasing AA content. As the AA concentration in the solution bath increases the transmittance increases from ≈ 5 to ≈28%. FTIR transmittance spectra of CuO have a characteristic stretching vibration mode of the metal–oxide bonds and the addition of AA caused the appearance of many peaks of this molecule. Contact resistance values decreased with the AA content from 0.657 × 109 to 0.342 × 109 Ω. It is worth noting that the deposition technique is low cost and very simple; obtained CuO thin films could be appropriate for different technological applications.