This study was conducted to investigate the developmental processes of tomato plants in greenhouses covered with polyethene agricultural film that applied a smart irrigation system. The study tested applying different irrigation water levels (IWLs) of 60, 80, 100, and 120% of crop evapotranspiration (ETc). Based on the findings for the tomato rows sampled to collect information about leaf area, biomass, and yield, maximal growth of tomatoes varied from 80 to 90 days after transplanting (DAT) for all IWLs. Among the applied IWLs, approximately 80% of ETc was recorded as the most appropriate for the crop growth rate (CGR), leaf area index (LAI), and yield, while the IWLs with 60%, 100%, and 120% of ETc also gave an equivalent output. The results of this work can provide useful information for farmers to make the right decisions about the amount of irrigation water to use.