Delegations from 94 countries and several international organizations were present during the inauguration in Caracas, the capital.
Among them were Cuban President Miguel Diaz-Canel; Bolivian President Evo Morales; President Daniel Ortega of Nicaragua, and President Salvador Sanchez Ceren of El Salvador.
Morales said: "Peoples and social movements have the historic mission of defending revolutionary processes through voting and conscience."
Fuat Oktay vice-president of Turkey, appeared on behalf of President Recep Tayyip Erdogan. Maduro spoke by phone with Erdogan, who reiterated his support for Venezuela.
He also expressed his desire to strengthen ties between the two nations, "as well as the work shared by the consolidation of a multipolar world, of justice, harmony and peace among nations."
Salvadoran President Ceren said: "The solidarity of the people and government of Venezuela had an invaluable moment with their quick help for El Salvador in the face of the devastating earthquakes that hit our country in 2001."
On Twitter, Cuban Foreign Minister Bruno Rodriguez said the delegation was in the land of the liberator Simon Bolivar to accompany the government and the Chavista people.
Nicaragua's President Ortega said he was honored to be in the homeland of Simon Bolivar, Hugo Chavez and of the heroic people fighting the battle for peace and justice in the region.
Prime Minister of Saint Vincent and the Grenadines Ralph Gonsalves; Vice President of Suriname Michael Ashwin Adhin and the Foreign Minister of Antigua and BarbudaEverly Paul Chet Greene were also present.
Chinese Minister of Agriculture Han Changfu attended as special envoy commanded by President Xi Jinping.
From Iran came Minister of Defense Amir Hatami, while Uruguay sent its Venezuela-based Charge d'Affaires Jose Luis Remedi.
Mexico sent its charge d'affaires at the Mexican Embassy in Caracas, Juan Manuel Nungaray, to represent the government of Andres Manuel Lopez Obrador (AMLO).
Secretary-General of the Organization of Petroleum Exporting Countries (OPEC) Mohammed Sanussi Barkindo was also among the delegates.
Maduro was re-elected May 20, 2018, with 5,823,728 votes or 67.7 percent of popular support, with 47.02 percent participation.