The protesters accuse 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 and others were arrested on Friday after being warned three times not to cross a police line outside the embassy. Those taken into custody included NAACP President Ben Jealous, Martin Luther King III, and actor and comedian Dick Gregory.
Several members of Congress also were arrested, including Massachusetts Representatives James McGovern and John Olver, Texas Rep. Al Green and Rep. Jim Moran of Virginia. They were handcuffed and placed into a US Secret Service van.
Clooney was released several hours later after paying a $US100 fine.
The arrests came after Clooney met this week with Obama, testified in the Senate and attended a state dinner for British Prime Minister David Cameron.
Clooney told AP before he was arrested that he could only hope to draw attention to the crisis in Sudan but that he didn't know if any progress had been made. He said he was impressed, though, with 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.
In a video footage provided by the Associated Press, Clooney comments upon his release: "What we're trying to achieve today was to bring attention to an ongoing emergency. The rainy season starts and a lot of people are going to die from it. Our job right now is trying to bring attention to it; one of those ways was apparently getting arrested. I guess we're not allowed to hang out on the Sudanese Embassy."
The actor said he asked Obama to involve China more in pushing for a solution in Sudan. A YouTube video Clooney recently posted online from his trip to Sudan appears 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 before his arrest. The situation is urgent, he said, because the upcoming rainy season would block transportation of food aid to the area.
Clooney said he didn't know if his actions would make a difference but that he at least wanted to make more people aware.
"It's such a silly thought to think you're actually succeeding in any of this," he said. "But if it's loud enough and you keep making it loud enough at the very least people will know about it, and you can't say we didn't know. That's the first step."