In Canada, over 90% of the paved roads are asphalt pavements. Most of these pavements were built decades ago, which are currently exhibiting a significant amount of surface distresses. These distresses includes potholes, rutting (deformation in the wheel path), and cracking. To repair these distressed pavements, the road agencies spend millions of dollars every year, of which a significant portion goes to acquiring new natural aggregates and asphalt. To reduce the rehabilitation cost, road agencies use up to 100% reclaimed asphalt pavements (RAP) in new construction. However, the asphalt available in recycled pavements is oxidized and stiffened due to various environmental processes which are susceptible to thermal and fatigue cracking. To soften and to decrease the viscosity of the RAP materials, various rejuvenators are being in practice. The rejuvenators are able to reactivate and restore the original properties of this long-term aged asphalt binder. Using Waste Cooking Oil (WCO) is one of the eco-friendly solutions which contains the similar lighter oil components of asphalt and can be used as an acceptable rejuvenator. Recent studies showed that WCO has an excellent potential to be used as a good rejuvenator in the hot mix asphalt (HMA) industry. This review article summarizes the performance and adverse effects of WCO as a rejuvenator.