A well optimised fuel injection timing enhances the combustion temperature and the rate of heat released in the cylinder. Fuel injections timing is sometimes used to optimised the combustion, performance and emissions characteristics of diesel engines. The study has experimentally investigated the effects of fuel injection timings on combustion, performance and emissions characteristics of a diesel engine running on propane and diesel fuels. In this research, both the pre- and main injections timings were advanced from 18^o (before top dead centre (bTDC)) pre-injection and 8^obTDC (main injection) to 21^oTDC (pre-) and 11^oTDC (main) and these were investigated by displacing 15% and 25% of the diesek fuel energy with propane. The results revealed that with the adjustment of the diesel injection timing to D21-11, there was huge improvement in the brake thermal efficiency and rise in the in-cylinder temperature. As regards the emissions, rise in tailpipe emissions of Carbon monoxide (CO) and total unburnt hydrocarbon (THC) were attributed to unburnt propane. Although, the presence of propane fuel led to low emission of NOx, increase cylinder temperature promoted by D21-11 injection timing resulted to increase in both NOx and NO₂ emissions