Methyl esters of castor oil derived carboxylic acids such as 10-undecenoic acid and ricinoleic acid are useful as biofuels, biolubricants and plasticizers. Esterification of these fatty acids was studied for the first time with near-critical and supercritical methanol without adding any external catalysts. Reaction kinetics were studied for esterification in a wide range of temperatures (523-673 K) and molar ratios (from 1 : 1 to 40 : 1) at a constant pressure of 20 MPa. Conversions of >90% were obtained for both the carboxylic acids within an hour of reaction time. Different kinetic models were developed and used to correlate the conversions at various temperatures and molar ratios. © The Royal Society of Chemistry.