The viscosity of palm biodiesel is a critical parameter that markedly affects in features consisting of injection rate, spray development, air-fuel mixing processes, thereby distinct impacts on the diesel engine performance characteristics. Determination of the trends in injection control is a core phase when employing biodiesel-diesel fuel blends, which inherently possess different fuel properties compared to diesel. This study focuses on investigating the correlation between variations in fuel properties of different palm biodiesel blend ratios and injection pressures to the corresponding changes in injection rate characteristics. Experiments were conducted with four test fuels: diesel (as the baseline) and three palm-biodiesel blends with 15%, 30%, and 60% biodiesel. Injection pressures, ranged from 400 to 1600 bar, were tested with a 1.5 ms injection duration and 45 bar back pressure. The results show that the injection timing is unaffected by the blend ratios, whereas the end of injection occurs earlier as the biodiesel content increases. The injection duration is notably shortened by approximately 13.6% as the injection pressure increases from 400 to 1600 bar. A minor decrease in the quasi-steady state injection rate was observed for a substantial viscosity difference of 20.7% between B60 and B0. However, a considerable decrease in the discharge coefficient of B60 compared to diesel, averaging 29.1%, was observed, attributed to flow resistance of higher-viscosity fuels.