Following a long tradition of Hollywood liberals, Penn was joined by Oliver Stone, Danny Glover and documentary maker Michael Moore in lauding the charismatic Venezuelan president after his death this week.
Only Penn appears to have made the trip to Caracas for the lavish funeral of Chavez -- who died aged 58 on Tuesday after a long battle with cancer -- but the others made their feelings quite clear.
JFK and Natural Born Killers director Stone, interviewed Chavez for a 2009 documentary South of the Border, called him "a great hero to the majority of his people and those who struggle throughout the world.
"Hated by the entrenched classes, Hugo Chavez will live forever in history," he added in a statement released after his death, adding: "My friend, rest finally in a peace long earned."
Glover, a long-time Afro-American activist and star of the Lethal Weapons films, praised Hugo Chavez as a "social champion," in a full-page statement issued by his publicist.
"I join with millions of Venezuelans, Latin Americans, Caribbeans (and) freedom-loving people around the world who embraced (him) as a social champion of people-centered democracy," he said.
Penn, wearing a black suit and tie, did not comment publicly at Friday's funeral, where he sat among the crowd of foreign dignitaries paying tribute to the leftist firebrand leader.
But in a statement after Chavez's death he said: "The people of the United States lost a friend it never knew it had. And poor people around the world lost a champion. I lost a friend I was blessed to have."
Their support for Chavez fits into a tradition of actors-turned-activists stretching back to Charlie Chaplin accused of communist sympathies, Jane Fonda in Vietnam, and up to George Clooney, arrested over Sudan last year.
Fonda was dubbed "Hanoi Jane" when she visited north Vietnam during the war there and accused of being anti-American.
Such outspoken political activism is not without its career or commercial risks for the actors or filmmakers involved -- especially when it runs counter to US interests.
"Americans in general want their stars to speak out praising what is right with America," said Steven Ross, a University of Southern California professor and expert on Hollywood's links with politics.
"They don't want to hear Jane Fonda, Sean Penn, Oliver Stone or Danny Glover telling us what is wrong with America or how foreign leaders such as Chavez, for all his limitations, have also furthered the cause of democratic reform."
Ross, author of Hollywood Left and Right: How Movie Stars Shaped American Politics, said the career costs vary.
He cited examples including Chaplin and Edward G Robinson, accused of being "premature anti-fascists" after World War II, and Harry Belafonte in the 1950s accused of participating in groups seen as being too far to the left.
More recently celebrities including Penn, Susan Sarandon, Tim Robbins and others spoke out against the 2003 Iraq war.
"In the case of the latter group, they managed to keep their careers. But Chaplin and Robinson found their careers as stars ended by being accused of Red sympathies."
Despite the risks, some in Hollywood are clearly happy to pin their political colors to the mast -- Penn, speaking before going to Caracas, threw his weight behind Chavez's chosen sucessor Nicolas Maduro.
"Venezuela and its revolution will endure under the proven leadership of Vice President Maduro," who faces elections within 30 days after formally taking over as interim president following Friday's funeral, he said.
Coincidentally, the issue was highlighted in Washington this week, when Republican Senator Rand Paul asked if it would have been right to order a drone strike on Fonda, as he led a nearly 13-hour filibuster in Congress.
"Is objecting to your government or objecting to the policies of your government sympathizing with the enemy?" Paul asked during his symbolic bid to block new CIA chief John Brennan's appointment over the use of drones.
"Some openly were sympathetic. No one will ever forget Jane Fonda swiveling around in North Vietnamese armored guns, and it was despicable.
But he said: "It's one thing if you're going to try her for treason, but are you just going to drop a drone hellfire missile on Jane Fonda?"