As president, Trump has the constitutional authority under Article I, Section 7 to reject a proposal from Congress.
Trump expressed pride in the Republicans who did not vote to support the resolution and said later that he had sympathy for those who defied him, adding they did what they had to do.
The president had threatened a veto of the resolution.
The Republican-controlled U.S. Senate voted to end his border emergency declaration, with 12 of Trump's fellow Republicans joining Democrats.
Opportunity rover left us with one last beautiful panorama of Mars
In a new post, NASA reveals what it says is the final " parting shot " that Opportunity captured before the dust storm killed it. The mission came to an end last summer when Opportunity became trapped in what eventually became a global dust storm on Mars.
Friday's veto ceremony fulfills Trump's pledged to thwart any effort by the Senate to block his emergency proclamation.
The emergency declaration is being challenged in court as an unconstitutional usurpation of Congress' power of the purse.
On 15 February Trump invoked the National Emergencies Act of 1976, claiming there was a crisis on the border that required the construction of walls to protect the United States.
After Trump signed the expected veto, US House Speaker Nancy Pelosi said the body planned to vote for a veto on March 26 on overriding Trump's move.
Twelve Republicans had defected from the president to ensure the state of emergency declaration's failure in the Senate. Mitt Romney, R-Utah, told reporters.
Residents warned as tropical cyclone Idai intensifies over Mozambique
A light aircraft has been dispatched with a team of specialists to Malawi to establish the exact humanitarian assistance required. This system turned around and once again came back to Mozambique Channel and received warmed waters resulting in strengthening.
"I think actually a national emergency was designed for a specific goal like this, so we have a great case", Trump said. "That shift has placed a substantial strain on border-security resources". The official was not authorized to speak publicly on internal deliberations so spoke on condition of anonymity. He cited "thousands and thousands" of gang arrests and claimed numerous asylum seekers released into the US were "stone-cold killers", ignoring data that shows immigrants are less likely to commit crime.
He also noted that despite record numbers of apprehensions at the border, there was not enough space to detain them all. He initially insisted that Mexico would pay for the wall but it has declined to do so.
Congress declined and the result was the longest shutdown in us history.
The declaration of an emergency allowed the administration to access over $6bn in additional funds not appropriated by Congress to build the wall.
The veto would be the first of Trump's presidency.
Full House episode eerily similar to real life scandal for Lori Loughlin
Becky puts an end to the scam, but justifies her husband's actions - he just wanted what's best for their twins. In the 26-year-old episode, Loughlin's character, Becky Katsopolis, faced a dilemma.