Algae are natural bioactive materials rich in protein, lipids, carbohydrates, vitamins, and elements (Fe, Mn, Zn, Cu, B, and Mo) hence; they have beneficial effects on plant growth. A field experiment was conducted to evaluate the influence of foliar spraying with different concentrations (0.5, 1.0, and 2.0 ml l^-1) of two algal species extracts including Amphora coffeaeformis (Bacillariophyta) and Pediastrum boryanum (Chlorophyta) on growth parameters, fruits yield, essential oil productivity, and chemical constituents of fennel plant during the two successive seasons (2019/2020 and 2020/2021). The results indicated that all treatments significantly affected all parameters compared to the control. Among the different concentrations used, the highest rate (2.0 ml l^-1) of Pediastrum boryanum caused the maximum significant increase in plant height, number of branches, number of umbels, fruits yield (g)/plant, the weight of 1000 fruits (g), essential oil percentage, yield (ml)/plant, components as well as nitrogen, phosphorus and potassium percentage in dry fruits. Therefore, using algae (A. coffeaeformis and P. boryanum) extract for enhancing yield and essential oil production is recommended.