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Ricinoleic acid is the main fatty acid constituent of castor oil which has antimicrobial activity. Research on the use of ricinoleic acid in ester form is more widely carried out, because it has a higher antimicrobial activity. In this study, fatty acid from hydrolysis and commercial ricinoleic acid was oxidized using KMnO4 before it was used for esterification. The ester synthesis was carried out by reacting oxidized products with acetic acid, lauric acid, or oleic acid (3:1) at 60°C for 6 hours using ZnCl2 as catalyst. The ester products were then characterized using FTIR and examined as antimicrobial assay against Staphylococcus epidermidis and Propionibacterium acnes. Emulsifier test was performed to observe the stability and emulsion type, using ester products as emulsifier. FTIR spectra showed a typical absorption band of C-O ester which indicates that oxidized fatty acid from hydrolysis ester and oxidized ricinoleic acid esters had been successfully formed. The antimicrobial activity assay showed positive results against the growth of Propionibacterium acnes and Staphylococcus epidermidis. Oxidized fatty acid from hydrolysis or ricinoleic-lauric ester showed the highest antimicrobial activity against Staphylococcus epidermidis. The emulsifier test showed the stability of six esters up to 24 hours for water-in-oil (w/o) emulsion type.