Secret Service Director Randolph “Tex” Alles said some 1,100 agents will hit their overtime allowance caps for the year.
Under Mr Trump, 42 people receive protection, an increase from 31 people during the Obama administration.
The Secret Service said it struggled with a “similar situation” last year.
Among those currently protected are 18 members of the Trump family, who have required security on international business trips to promote Trump properties as well as family holidays.
Some of the bills, according to the USA Today report, include:
Other trips requiring security included visits in February by both Eric Trump and Donald Trump Jr to Vancouver, British Columbia, to open a new Trump hotel there, and to Dubai for the opening of a Trump International Golf Club.