The Soviet and Chinese Aid Missions established in 1958 and 1959 were the first important non-Muslim presence in north Yemen. Following the September 1962 revolution, the Yemen Arab Republic became closely allied with and heavily dependent upon Egypt. Saudi Arabia aided the royalists in their attempt to defeat the Republicans and did not recognize the Yemen Arab Republic until 1970. Subsequently, Saudi Arabia provided Yemen substantial budgetary and project support. At the same time, Saudi Arabia maintained direct contact with Yemeni tribes, which sometimes strained its official relations with the Yemeni Government. Hundreds of thousands of Yemenis found employment in Saudi Arabia during the late 1970s and 1980s.

In February 1989, north Yemen joined Iraq, Jordan, and Egypt informing the Arab Cooperation Council (ACC), an organization created partly in response to the founding of the Gulf Cooperation Council, and intended to foster closer economic cooperation and integration among its members. After unification, the Republic of Yemen was accepted as a member of the ACC in place of its YAR predecessor. In the wake of the Gulf crisis, the ACC has remained inactive. Yemen is not a member of the Gulf Cooperation Council.

British authorities left southern Yemen in November 1967 in the wake of an intense terrorist campaign. The people's democratic Republic of Yemen, the successor to British colonial rule, had diplomatic relations with many nations, but its major links were with the Soviet Union and other Marxist countries. Relations between it and the conservative Arab states of the Arabian Peninsula were strained. There were military clashes with Saudi Arabia in 1969 and 1973, and the PDRY provided active support for the Dhofar rebellion against the Sultanate of Oman. The PDRY was the only Arab state to vote against admitting new Arab states from the Gulf area to the United Nations and the Arab League. The PDRY provided sanctuary and material support to various international terrorist groups.

Yemen is a member of the United Nations, the Arab League, and the organization of the Islamic conference. Yemen participates in the nonaligned movement. The Republic of Yemen accepted responsibility for all treaties and debts of its predecessors, the YAR and the PDRY. Yemen has acceded to the nuclear nonproliferation treaty. The Gulf crisis dramatically affected Yemen's foreign relations. As a member of the UN Security Council (UNSC) in 1990 and 1991, Yemen abstained on a number of UNSC resolutions concerning Iraq and Kuwait, and voted against the "use of force resolution." Western and Gulf Arab states reacted by curtailing or canceling aid programs and diplomatic contacts. At least 850,000 Yemenis returned from Saudi Arabia and the Gulf.

Subsequent to the liberation of Kuwait, Yemen continued to maintain high-level contacts with Iraq. This hampered its efforts to rejoin the Arab mainstream and to mend fences with its immediate neighbors. In 1993, Yemen launched an unsuccessful diplomatic offensive to restore relations with its Gulf neighbors. Some of its aggrieved neighbors actively aided the south during the 1994 civil war. Since the end of that conflict, tangible progress has been made on the diplomatic front in restoring normal relations with Yemen's neighbors. The Omani-Yemeni border has been officially demarcated. In the summer of 2000, Yemen and Saudi Arabia signed an International Border Treaty settling a 50-year-old dispute over the location of the border between the two countries. Yemen also settled its dispute with Eritrea over the Hanish Islands in 1998.