Fennel, Foeniculum vulgare Mill., is one of the umbelliferous medicinal plants and is subjected to infection by Sclerotinia sclerotiorum (Lib.) de Bary, causing economic losses in plant stand and yield in Egypt. Biological control of S. sclerotiorum using algal filtrates of Nostoc spp., Oseillatoria spp., Spirulina platensis, Chlorella spp., Anabaena oryzae, Wollea spp., Anabaena flos-aquae and N. humifusum as well as the commercial biocides namely, Rhizo-N, Plant guard, Bio-ARC and Bio-Zeid were evaluated under laboratory and greenhouse conditions. All the tested algal filtrates, except those of Anabaena oryzae and Wollea spp., have significantly reduced the mycelial growth of S. sclerotiorum. However, filtrates of Nostoc spp., Oseillatoria spp. and S. platensis completely inhibited the radial growth of the fungus and significantly decreased damping-off percentages and increased length of shoot-and root systems, plant fresh weight and number of branches/plant. All the used biocides have significantly reduced the radial growth of S. sclerotiorum. Rhizo-N gave the highest inhibition followed by Plant guard. The least inhibition of S sclerotiorum growth was recorded by Bio-ARC and Bio-Zeid. Rhizo-N decreased damping-off percentages and increased the length of shoot and root systems, plant fresh weight and number of branches/plant.