The PARTNERS Act directs the Secretary of Defense to establish a military training pilot program with Mexico to help build the capacity of Mexican armed forces to combat transnational criminal organizations operating in both countries. The program would focus on joint operations and training in areas such as network analysis, counter-threat financing, and efforts to disrupt drug, weapons, and human trafficking. Within 180 days of the bill's enactment, the Defense Department must submit a five-year implementation plan to Congress that includes estimated program costs and coordinates with the State Department and other civilian agencies involved in counter-narcotics and counterterrorism work. The legislation affects both the U.S. military and Mexican armed forces, as well as law enforcement agencies dealing with transnational criminal threats. While the bill does not specify funding amounts in the provided text, it requires the Defense Secretary to detail all administration costs for the five-year pilot period in the congressional plan.