In the latest incident, a rock was thrown through the window of the Republican presidential nominee's field office, CNN affiliate KCNC
Earlier in the day, words describing Trump in derogatory terms were painted on a wall at the office.
Denver Police Department spokesman Tyrone Campbell said a possible suspect was being held in connection with the latest incident.
"We are investigating a second incident of vandalism in the city at Donald Trump's office," he said. "The first vandalism case occurred Friday morning and both cases are under investigation for criminal mischief. '
The person being held had not been identified late Friday.
CNN has attempted to contact the Trump campaign for a comment.
Contest often has been heated
Friday's incident was the latest in a number involving property associated with both Trump and Democratic presidential candidate Hillary Clinton during an often heated race for the White House.
The front entrance of Trump's new Washington hotel was vandalized with spray-painted messages which read "Black Lives Matter" and "No Justice No Peace."
Clinton, who has met with Black Lives Matter protesters, told a presidential debate audience that Trump "has a long record of engaging in racist behavior."
In another incident, Trump's star on Hollywood's Walk of Fame was defaced
White powder was mailed to Clinton's campaign office in New York. It tested negative for harmful substances but prompted a temporary evacuation of one part of the office, which remained open.
Colorado is a key battleground state in the presidential election.