Transient emissions of a turbocharged three-litre V6 diesel engine fuelled by hydrogenated vegetable oil (HVO) blends were experimentally investigated and compared with transient emissions of diesel as reference. The transient emissions measurements were made by highly-dynamic emissions instrumentations including Cambustion HFR500, CLD500 and DMS500 particulate analyzer. The HVO blends used in this study were 30% and 60% of HVO in diesel by volume. The transient conditions were simulated by load increases over 5 s, 10 s and 20 s durations at a constant engine speed. The particulate, NO, HC concentrations were measured to investigate the mechanism of emission formation under such transient schedules. The results showed that as the load increased, NO concentrations initially had a small drop before dramatically increasing for all the fuels investigated which can be associated with the turbocharger lag during the load transient. Also, as the load increase period was increased, the peak value of particle numbers and particulate mass declined apparently and the particle sizes became smaller. The HVO blends had lower particulate and HC concentrations under various test conditions compared with diesel, but they had higher NO concentrations. Under the transient load condition, HVO blends had more particulate concentration in nucleation mode while HVO blends produced less and smaller particulate matters in accumulation mode compared to diesel.