The aim of the present study was to analyze the performance, emission and combustion characteristics at variable compression ratio (VCR) of compression ignition (CI) engine using a suitable biodiesel blends as fuel. The biodiesel selected to conduct the experimental investigation was jatropha. The selection of biodiesel was done on an extensive review of literature which indicated that these could be used as fuel on a VCR diesel engine. The experimental study was conducted on a four stroke, VCR diesel engine using above biodiesel by making their blends with diesel. The thermal performance and emissions characteristics were evaluated by operating the engine at compression ratios (CRs) of 18, and varying loads from 25%, 50%, 75% and 100% of full load. The thermal performance parameters evaluated were brake thermal efficiency (BThE), brake specific fuel consumption (BSFC) and exhaust gas temperature (ExGT). The emission constituents measured were carbon monoxide (CO), unburned hydrocarbons (HC) and oxides of nitrogen (NOx). The BSFC was reduced with increase in load whereas diesel and biodiesel blends curve were close to each other at 100 % load. The BThE was found maximum in diesel and minimum in case of J50 biodiesel blend at all loads. The ExGT was also increased as increase in load. The emission characteristics evaluation indicated that the blend J50 gave minimum harmful emissions amongst all the blends. Further, at a higher CR of 18 fairly reduced exhaust emissions were observed irrespective of blend. The difference in performance between biodiesel blends and diesel reduced at 100 % load at CR 18. i.e. the operation of the engine fuelled with biodiesel blends tends towards that fuelled with diesel.