Penn, whose real name is Kalpen Modi, was in the Dupont Circle area of the US capital when a gunman stole his wallet and other belongings on Tuesday.
Penn's former publicist Jennifer Goodwin confirmed a report on TMZ.com that Penn was robbed, the Chicago Tribune reported.
According to a police crime summary, an armed robber forced a victim to lie on the ground and give up his cell phone and other possessions.
It, however, did not include names, the paper said. Penn played Kumar in the movie Harold and Kumar Go to White Castle and had a recurring role on the Fox show House.
He has been working in the White House's Office of Public Liaison Associate Director in its Office of Public Engagement for less than a year, focusing on connecting US President Barack Obama with the Asian-American and Pacific Islander communities.
It was reported that Penn was planning to leave the White House to resume his acting career, with a Christmas-themed Harold and Kumar movie in the pipeline.
Penn was a prominent campaigner during President Obama's 2008 White House bid, and was offered a job in the administration in 2009.
Photograph: Jonathan Ernst/ Reuters