The escalation in environmental concerns in the construction industry forces many construction companies to implement reverse logistics (RL). The implementation helps the companies comply with environmental regulations, enhance their competitiveness, and contribute to sustainability in construction. Nevertheless, companies face many challenges in utilizing their scarce resources to perform RL activities in practice. Thus, many of them have chosen to outsource RL activities and focus on their core business. Although the RL outsourcing topic has received significant attention from both academia and practice, there are few studies on the role of the cooperation between firms and their reverse logistics service providers (RLPs) in reverse logistics outsourcing performance (RLOP) improvement. This research aims to investigate the different impacts of construction companies’ cooperation on RLOP. The study employs Partial Least Squares Structural Equation Modelling (PLS-SEM) to analyze 173 responses collected from Australian construction firms. The results indicate that cooperation not only directly affects RLOP but also plays a mediating role in the relationship between other factors and RLOP. Specifically, long-term orientation, trust, dependence, and planning indirectly impact RLOP through cooperation. The insights can be beneficial for both firms and their RLPs.