People who are in the United States illegally and are accused of theft and violent crimes would have to be detained and potentially deported even before a conviction.
The measure quickly passed the new Republican-controlled Congress with some Democratic support even though immigrants rights advocates said it possibly could lead to large round-ups of people for offences as minor as shoplifting.
Trump has pledged that his administration will carry out the largest mass deportation effort in US history.
Trump, who won back the White House by tapping into public anger over illegal immigration, has made the promised crackdown a centrepiece of his political career.
Democratic Senator John Fetterman has called the Laken Riley Act "common sense". (AP PHOTO)
"This shows the potential for additional enforcement bills that will help us crack down on criminal aliens and totally restore the rule of law in our country," Trump told House Republicans at a conference at his Doral golf club in Florida.
The legislation is named for Laken Riley, a 22-year-old Georgia nursing student who went out for a run in February 2024 and was killed by Jose Antonio Ibarra, a Venezuelan citizen in the US illegally.
Ibarra was found guilty in November and sentenced to life without parole.
"To have a bill of such importance named after her is a great, a great tribute," Trump said.
"This new form of crime, criminal, illegal aliens, it's - it's massive, the numbers are massive and you add that to the crime we already had".
The swift passage of the legislation and Trump's signing nine days after taking office adds to the potent symbolism for conservatives.
To critics, the measure has taken advantage of a tragedy and could lead to chaos and cruelty while doing little to fight crime or overhaul the immigration system.
Democratic Senator John Fetterman, a co-sponsor, planned to attend the signing ceremony.
"I believe a secure border creates a more secure nation and it's just common sense," he said in a statement, adding that he was elected "to work with both sides of the aisle".
Federal officials would have to detain any immigrant arrested or charged with crimes such as theft or assaulting a police officer, or offences that injure or kill someone.
Ibarra had been arrested for illegal entry in September 2022 near El Paso, Texas, and released to pursue his case in immigration court.
Federal officials say he was arrested by New York police in August 2023 for child endangerment and released.
Police say he was also suspected of theft in Georgia in October 2023 - all of which occurred before Riley's killing.
After the House passed the bill, Republican House Speaker Mike Johnson said it was "the right thing to do".
Some Democrats have questioned whether it is constitutional.
Immigrant advocates are bracing for mass detentions that they say will mean costly construction of immigration lockup facilities to house the people arrested.
"They don't just get to celebrate. They get to use this for their mass deportation agenda," Naureen Shah of the American Civil Liberties Union said of the act's supporters.
The ALCU says the act can allow people to be "mandatorily locked up - potentially for years - because at some point in their lives, perhaps decades ago, they were accused of non-violent offences".
The signing follows a flurry of first-week executive orders by Trump that are designed to better seal off the US-Mexico border and eventually move to deport millions of immigrants without permanent US legal status.
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