Phytophthora capsici is a plant pathogenic oomycete that causes significant damage to many crops, including black peppers, chili, cucurbits, and tomatoes. This pathogen is widespread and can survive in soil and plant debris for several years, making it difficult to control. The aim of the research was to observe the effectiveness of three essential oils as nano-emulsion formulas (NS, NC, NE and NA) against the growth of P. capsici in vitro and in vivo. In vitro testing was carried out using 2 methods, namely the poison food and volatile disc assay. Testing of active ingredients using the GCMS method and measuring active ingredient particles using the DLS method. In vivo testing was carried out on chili seeds to determine their growth and germination. The result indicated that all nano-emulsions at 0.50% inhibited the growth of P. capsici which varied between 33,25% to 88,50%. The NC, NS, and NA formula caused complete mycelial growth inhibition at a concentration of 1.0%. Total inhibition of growth also occurred with volatile compounds produced by NS and NA formula. The NC, NS, NE and NA formulas are not phytotoxicity to chili seeds and their germination. Therefore, three essential oils (NC, NS, NE) and the mixture of them (NA) are potential to be used in managing P. capsici as eco-friendly control and possibly as an alternative to synthetic fungicides.