Biodiesel is considered as one of the prime sources of non conventional transportation fuels. Though there are various sources available for biodiesel production, algal oil holds importance since it is non-edible and abundantly available. In this study, we carried out transesterification of oil extracted from marine algae using nano calcium oxide catalyst. Nano calcium oxide catalyst was produced by calcinating clam shell powder. Algae biomass were collected from coastal areas near Chennai, dried, crushed and sieved for uniform sized particles. Transesterification experiments were carried out using extracted oil from algal biomass using hexane as a solvent. Effects of oil to methanol ratio, temperature and catalyst loading were analyzed and the optimum values were determined. FAME analysis was done to qualify and quantify the biodiesel yield. Experimental results showed that algal oil is a good source of oil and nano CaO catalyst is an effective catalyst for transesterification.