The protesters accused Sudanese president Omar al-Bashir of provoking a humanitarian crisis and blocking food and aid from entering the Nuba Mountains in the county’s border region with South Sudan.
Clooney, his father, Nick Clooney, and others were arrested after being warned three times not to cross a police line outside the embassy. Those taken into custody included civil rights leaders Ben Jealous, Martin Luther King III, and actor and comedian Dick Gregory.
Several members of Congress also were arrested. They were handcuffed and put into a United States Secret Service van. Clooney was released several hours later after paying a $100 (£63) fine.
Clooney met Mr Obama this week, testified in the Senate and attended a state dinner for Prime Minister David Cameron.
Clooney said before he was arrested that he could only hope to draw attention to the crisis in Sudan but that he did not know if any progress had been made. He said he was impressed, though, with Mr Obama’s engagement on the issue.
“It’s amazing to sit down with a world leader who knows all of the intricacies of what’s going on in Sudan,” he said.
The actor said he asked Mr Obama to involve China more in pushing for a solution in Sudan. A YouTube video Clooney recently posted online from his trip to Sudan appeared to show a Chinese-made missile being used against the Nuba community.
Clooney said international leaders need to “follow the money” flowing to Sudan’s leaders to expose corruption.
“This is a moment where we have a chance to do something because if we don’t, in the next three to four months, there’s going to be a real humanitarian disaster,” Clooney said.