Pieces of plywood covered the graffiti Sunday afternoon. Video spreading on social media showed the man marking the building and walking away.
According to D.C. police, the man spray-painted the hotel just after 4:00 p.m. Saturday. No suspects have been identified, according to WJLA.
Patricia Tang, the director of sales and marketing for the Trump International Hotel in D.C., said, "The matter is under investigation, and we have no comment at this time."
"I'll give you an example," Trump said. "We're just opening up on Pennsylvania Avenue right next to the White House, so if I don't get there one way, I'm going to get to Pennsylvania Avenue another.
"But we're opening the Old Post Office. Under budget, ahead of schedule, saved tremendous money. I'm a year ahead of schedule. And that's what this country should be doing."