Biofuel from plant oils have attracted a great attention as replacements for conventional diesel to decrease reliance on fossil based-oil and offer an eco-friendly fuel. The transesterification reaction of cottonseed oil with isopropyl alcohol using potassium hydroxide as catalyst has been deliberated for the production of biodiesel. The objective of this study is to find the best condition for the production of isopropyl esters of cottonseed oil. The reaction parameters used are isopropyl alcohol/cottonseed oil molar ratio (6:1 up to 30:1 in interval of 3), catalyst amount (0.5-2.5 wt. ) and heating events of (50-80 °C) while the duration of the procedure and the stirring power are fixed at 2 hour and 600 rpm, respectively. However, about 98.9 of fatty acid isopropyl esters was obtained at the best conditions of 2 h, 600 rpm, 1.5 catalyst concentration, 70 oC temperature of the reaction and 1:24 as cottonseed oil to isopropyl alcohol molar ratio. © 2016 The Authors.