Najib's week-long trip marks another potential setback for Washington's "pivot" toward Asia, two weeks after President Rodrigo Duterte of longtime US ally the Philippines visited China with olive branch in hand.
Meeting at Beijing's Great Hall of the People, Najib and his Chinese counterpart Li Keqiang witnessed the signing of nine agreements spanning defence, business and other spheres.
"I believe this visit will bring our bilateral ties to a new high... a historic high," Najib said prior to meeting with Li.
Asked for details of the defence arrangement, Chinese vice foreign minister Liu Zhenmin said that the two countries were "focusing on naval cooperation," adding that the deal "marks a big event in our bilateral ties."
China and Malaysia have an outstanding territorial dispute in the South ChinaSea, which is claimed almost in its entirety by Beijing.
Parts of the vast maritime region are also claimed by the Philippines and Vietnam, among others, who have found themselves caught in an increasingly tense dispute between the US and China over Beijing's construction of military-capable artificial islands in the region.
"China and Malaysia are littoral states of the South China Sea so we need to enhance our cooperation to ensure peace and stability in the South China Sea and enhance our mutual trust," Liu said.
