Rubio, the Republican senator from Florida, is among the least controversial of Trump's nominees and vote was decisive, 99-0 on Monday.
Another pick, John Ratcliffe for CIA director, is also expected to have a swift vote. Action on others, including former combat veteran and Fox News host Pete Hegseth for defence secretary, is expected later in the week.
Marco Rubio will be the nation's top diplomat and the first Latino to hold the position. (AP PHOTO)
"Marco Rubio is a very intelligent man with a remarkable understanding of American foreign policy," Senator Chuck Grassley of Iowa, the senior-most Republican, said as the chamber opened.
It's often tradition for the Senate to convene immediately after the ceremonial pomp of the inauguration to begin putting the new president's team in place, particularly the national security officials.
During Trump's first term, the Senate swiftly confirmed his defence and homeland security secretaries on day one, and President Joe Biden's choice for director of national intelligence was confirmed on his own Inauguration Day.
With Trump's return to the White House, and his Republican Party controlling majorities in Congress, his outsider Cabinet choices are more clearly falling into place, despite initial scepticism and opposition from both sides of the aisle.
Senate Majority Leader John Thune moved quickly Monday, saying he expected voting to begin "imminently" on Trump's nominees.
Democrats are holding their opposition for some of Trump's other picks who have less support, including Tulsi Gabbard for director of national intelligence and vaccine sceptic Robert F Kennedy Jr for health secretary.
Senate Democratic Leader Chuck Schumer said his party will "neither rubber-stamp nominees we feel are grossly unqualified, nor oppose nominees that deserve serious consideration".
Rubio, he said, is an example of "a qualified nominee we think should be confirmed quickly".
Rubio, a well-liked senator and former Trump rival during the 2016 presidential race, has drawn closer to the president in recent years.
As secretary of state, Rubio would be the nation's top diplomat, and the first Latino to hold the position. Born in Miami to Cuban immigrants, he has long been involved in foreign affairs, particularly in South America, and has emerged as a hawk on China's rise.
During his confirmation hearing last week, Rubio warned of the consequences of America's "unbalanced relationship" with China.
While he echoes Trump's anti-globalist rhetoric, Rubio is also seen as an internationalist who understands the power of US involvement on the global stage.
Rubio will over from outgoing Secretary of State Antony Blinken, who has said he hopes the Trump administration continues Biden's policies in the Middle East to end the war in Gaza and to help Ukraine counter Russian nomination.
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