β-Gallium oxide (Ga2O3) has received intensive attention in the scientific community as a significant high-power switching semiconductor material because of its remarkable intrinsic physical characteristics and growth stability. This work reports the heteroepitaxial growth of the β-Ga2O3 ultrathin film on a sapphire substrate via mist chemical vapor deposition (CVD). This study used a simple solution-processed and nonvacuum mist CVD method to grow a heteroepitaxial β-Ga2O3 thin film at 700 °C using a Ga precursor and carrier gases such as argon and oxygen. Various characterization techniques were used to determine the properties of the thin film. Additionally, a computational study was performed to study the temperature distribution and different mist velocity profiles of the finite element mist CVD model. This simulation study is essential for investigating low to high mist velocities over the substrate and applying low velocity to carry out experimental work. XRD and AFM results show that the β-Ga2O3 thin film is grown on a sapphire substrate of polycrystalline nature with a smooth surface. HR-TEM measurement and UV-visible transmission spectrometry demonstrated heteroepitaxial β-Ga2O3 in an ultrathin film with a band gap of 4.8 eV.