After being warned not to cross a police line three separate times, they were handcuffed and placed into a US Secret Service van, the Associated Press reported. Several hours later Clooney paid a $100 fine and was released.
Protesters say Sudan's President Omar al-Bashir has provoked a humanitarian crisis and blocked aid from entering the Nuba Mountains, a border region near South Sudan.
NAACP President Ben Jealous, Martin Luther King III, and comedian Dick Gregory were also arrested, the AP wrote. The congressmen included Massachusetts Reps. James McGovern and John Olver, Texas Rep. Al Green and Rep. Jim Moran of Virginia.
After his release from a Washington police station, Clooney said "the real looming danger is that ... tens of thousands of people are going to die from starvation that is man made. This isn't a famine, this is a man made tragedy."
Clooney testified before the Senate and met with President Barack Obama earlier this week to discuss the crisis, said CNN.
The Washington Post reported that Clooney and the gathered activists, congressmen, and religious leaders spoke of Sudan's humanitarian crisis.
Clooney recently returned from Sudan and has been working with The Enough Project, a human rights advocacy group, to bring attention to the issue.