"Quite an evening in DC. Secret Service and Law Enforcement did a fantastic job. They acted quickly and bravely," Trump posted on his Truth Social platform.
"The shooter has been apprehended, and I have recommended that we 'LET THE SHOW GO ON' but, will entirely be guided by Law Enforcement."
Trump was expected to give a statement at the White House.
A person is in custody after a "shooting incident" near a security checkpoint at the correspondents' dinner, authorities said.
A law enforcement official said an officer was shot in a bullet-resistant vest but is expected to be OK.
Trump was uninjured. Authorities said the incident occurred outside the ballroom where Trump and other guests were seated.
The secret service and other authorities swarmed the banquet hall at the Washington Hilton on Saturday, local time, as guests dining on burrata salad ducked under tables by the hundreds.
"Out of the way, sir!" someone yelled. Others shouted to duck. From one corner, a "God Bless America" chant began as Trump was escorted off stage.
He fell briefly - he apparently tripped - and was helped up by secret service agents.
A law enforcement official confirmed there was a shooter but no further details were immediately available.
The White House Correspondents' Association president said everyone was safe after the shooting incident and the event will be rescheduled.
Some in the crowd reported hearing what they believed to be five to eight shots fired.
The banquet hall - where hundreds of prominent journalists, celebrities and national leaders were awaiting Trump's remarks - was immediately evacuated.
Members of the National Guard took up position inside the building as people were allowed to leave but not immediately re-enter.
Those in attendance included Trump, Vice President JD Vance, Defence Secretary Pete Hegseth and Secretary of State Marco Rubio - and many other leaders of the Trump administration.
Outside the hotel, members of the National Guard and other authorities flooded the area as helicopters circled overhead.
Generally, the Hilton hotel, where the dinner has taken place for years, remains open to regular guests during the White House Correspondents' Dinner, and security has typically been focused on the ballroom rather than the hotel at large, with little screening for people not entering the dinner itself.
In past years, that has created openings for disruptions in the lobby and other public spaces, including protests in which security moved to remove guests who unfurled banners or staged demonstrations.
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