Capitol officers said the machete was spotted by an X-ray machine at an entrance to the building’s visitor centre and the suspect’s motives are not yet clear.
But with security already on high alert after the recent attempt on the life of Mr Trump in the run up to November’s election, authorities revealed that the knives were found during a search of the man’s bag.
In a statement posted online, police said the suspect, who has not been named, was arrested on multiple charges of carrying a dangerous weapon.
His detention on Wednesday came shortly before a visit by President-elect Trump, who was meeting Senate Republicans.
Mr Trump also later viewed the casket of former President Jimmy Carter, who is lying in state in the Capitol Rotunda, a large room in the centre of the building which contains both the US House and Senate chambers.
Capitol Police said they arrested the man shortly after 2pm local time as he was attempting to go through security at the Capitol Visitor Centre.
“Our officers spotted a machete in the man’s bag, stopped the X-ray machine, arrested the man, and secured the machete,” the agency said, adding that it also found three knives in his bag.
The arrest came as members of the public were streaming into the Capitol to pay their respects to former President Carter during his period of lying in state.
There had been increased security around the Capitol complex in Washington DC this week, as lawmakers met on Monday to certify the results of the 2024 presidential election.
Earlier, in a separate incident, a 35-year-old man from Virginia was arrested for ‘Unlawful Activities’ after he attempted to set his car on fire on First Street Northwest near the Grant Memorial, according to Capitol Police.
Officers said the man lit a bag on top of his car, and the bag extinguished itself as officers ran to the man. He was then arrested.
The vehicle was declared suspicious and removed for investigation.
