Lignin is a natural, aromatic polymeric material that accounts for about 25–30% of woody biomass. Recent research has shown the potential benefits of lignin in reducing the carbon footprint of the roading industry, and improvements in the performance of asphalt pavements. This work investigated the effect of a softwood (Pinus radiata) and a hardwood lignin (Eucalyptus globulus) on some key performance properties of bituminous binders. Rheological tests on the control bitumen and two lignin-modified bitumen blends at 20% concentration were conducted along with the particle sizing of the lignin materials themselves. Although the addition of lignins improved the rutting resistance of the blends, with hardwood being much more beneficial in this scenario, the crack resistance of the blends was compromised. The lignin-modified blends oxidised more than the control binder. Overall, the results of this study showed the addition of hardwood lignin was more beneficial than the softwood lignin. The interrelationship of different rheological parameters was investigated and the influence of ageing on the bituminous binders was discussed.