Quasi-steady gas-phase combustion of Jatropha bio-diesel in a mixed convective air environment is studied both experimentally and numerically. Porous sphere experiments have been conducted to measure the mass burning rates and observe the flame shapes of spherical particles fed with bio-diesel. A numerical model has been developed to simulate the experiments. The Jatropha bio-diesel has been considered as a single component fuel (C18H34O2). Transient governing equations in the gas-phase alone are solved through the finite volume approach employing non-orthogonal control volumes in a semi-collocated mesh. Thermo-physical properties are evaluated based on the local temperature and the species concentrations. A single step global reaction with five species (C18H34O2, O2, N2, CO2 and H2O) is employed to model the finite rate kinetics. Results have been obtained for a range of mixed convective flow conditions. Comparisons of the results with those of diesel combustion have been made in few cases. It is observed that the burning rate of bio-diesel is less by about 11% than those for diesel for the same air velocity and sphere size. © 2008 Elsevier Ltd. All rights reserved.