The order imposes stringent regulations on many potential immigrants, suspends all refugee admissions for four months and authorizing "extreme vetting", ABC.net.au reported.
"I'm establishing new vetting measures to keep radical Islamic terrorists out of the United States of America. Don't want them here," Mr Trump said.
"We only want to admit those into our country who will support our country and love deeply our people."
The order directs the State Department to stop issuing visas to Syrian nationals and halts the processing of refugees from the war-torn country indefinitely, stating that their entry is "detrimental to the interests of the United States".
The program will be suspended until their admission to the country is "consistent with the national interest".
In addition, America's broader refugee admissions program has been suspended for four months so a review can take place on how refugees are vetted.
Read alsoMcCain ahead of Trump-Putin phone talks: Russian president "a murderer and a thug"The temporary halt to refugee processing will eventually give priority to minority religious groups fleeing persecution.
Mr Trump said the exception would help Syrian Christians fleeing the civil war there but legal experts said singling out a particular religion could be challenged as a violation of the U.S. Constitution.
Read alsoTrump’s advisor confirms anti-Russian sanctions lift being consideredMr Trump had promised the vetting measure during last year's election campaign, saying it would prevent militants from entering the United States from abroad.
