Following the attacks of September 11th, public and private entities recognized a need to protect the global supply chain from terrorist disruption. In response to this need, the U.S. Government partnered with industry to create the Customs-Trade Partnership Against Terrorism (C-TPAT) program. This research investigates the public–private partnership (PPP) relational aspects of C-TPAT. C-TPAT encourages firms to voluntarily improve their security competence and that of their supply chain partners. We introduce the concept of relational security in the context of PPPs. We define relational security as all activities that establish, cultivate, and maintain successful security exchanges between parties. We establish C-TPAT as one indicator of relational security by demonstrating its ability to establish, cultivate, and maintain successful security exchanges between parties. Results indicate certified firms outperform noncertified firms in security performance, firm performance, and resilience.