Candida antarctica Lipase B (CALB) immobilized onto iron magnetic nanoparticles was evaluated as biocatalyst for the synthesis of flavor esters. Methyl and ethyl butyrate were synthesized by esterification of butyric acid with methanol and ethanol, respectively, in a medium containing solvent. The nanoparticles were produced by the co-precipitation method. The process parameters (type of solvent, temperature, substrate concentration, molar ratio, amount of biocatalyst, stirring speed and reaction time) were studied. The optimum conditions for both esters were achieved at 25 °C, 0.5 mol/L (methyl butyrate) and 0.4 mol/L (ethyl butyrate), molar ratio of 1:1, amount of biocatalyst: 10 mg, 150 rpm and 8 h of reaction, using heptane as solvent. Under those conditions, the maximum conversions of methyl butyrate and ethyl butyrate were higher than 90 %. The synthesis of flavor esters was also conducted by using Novozym® 435, a commercial catalyst, for comparison purposes.