Moisture damage occurs due to loss of cohesion and/or adhesion, which results in loss of stiffness and strength. Currently, the surface free energy (SFE) approach is used to calculate mixture performance in terms of various SFE parameters to assess moisture susceptibility of various newly developed binders. In the present study, the concept of SFE is used to evaluate the moisture-induced damage potential of newly modified bitumen using high-density polyethylene (HDPE) pyro-oil. For this purpose, parameters of SFE considered are work of adhesion, work of cohesion, wettability, and energy ratio (ER). HDPE pyro-oil was obtained from pyrolysis process at 750°C. For determination of surface tension properties of base and modified bitumen, this study used glycerol, formamide, and distilled water as probe liquid, and a sessile drop method was adopted to measure the static contact angle. The aggregates considered in this study were basalt, gravel, and limestone. Dispersive and polar components of aggregates were directly taken from the literature. In contrast, for base bitumen (VG30) and pyro-oil–modified bitumen (POMB), these components were determined using van Oss–Chaudhury–Good theory. Along with this, the variation in contact angle, SFE components and surface tension parameter of base and modified bitumen were studied for different time of ageing (0, 45, 85, and 150 min) using rolling thin film oven (RTFO) as per guidelines of Superpave. The investigation concludes that, for the parameters under study, the analysis of data does not show any regular pattern. Work of adhesion decreases whereas work of cohesion increases with ageing resulting in increased moisture susceptibility for pyro-oil–modified bitumen. Further, the results showed that pyro-oil was effective in enhancing the surface tension parameter as compared to the base binder for different ageing conditions. Based on the results of energy ratio, it is concluded that a combination of the binder with basalt gives higher resistance to moisture damage than limestone and gravel.