Waste cooking oil (WCO) was used as bio-diesel feedstock. WCO with methanol was heated at different temperature with the help of conventional mechanical stirrer. Potassium hydroxide (KOH) and sodium hydroxide (NaOH) was used as catalyst. The effect of different operational parameters such as, catalyst loading, reaction temperature, and reaction time were evaluated. From the results, it was clear that the bio-diesel fuel produced from waste cooking oil (WCO) was within the recommended standards of biodiesel fuel. The trans-esterification reaction using potassium hydroxide (KOH) catalyst was more effective than sodium hydroxide (NaOH) catalyst for the higher yields conversion. With potassium hydroxide 0.4 wt. %, yield was 94.4% and conversion was 97.76% at 60o C, in three hours reaction time.