The photo has received sweeping bipartisan disapproval. Griffin and celebrity photographer Tyler Shields, who took the photo, posted it on their social media accounts Tuesday.
In an attempt to appease those who were offended by the image, the controversial comedian then tweeted, "OBVIOUSLY, I do not condone ANY violence by my fans or others to anyone, ever! I'm merely mocking the Mocker in Chief."
That did little to placate her critics, prompting Griffin to tweet a video of herself apologizing.
"Hey, everybody, it's me, Kathy Griffin," she says in the video. "I sincerely apologize. I am just now seeing the reaction to these images. I'm a comic. I crossed the line. I move the line. Then I cross it. I went way too far. The image is too disturbing. I understand how it offends people. It wasn't funny. I get it. I've made a lot of mistakes in my career. I will continue. I ask your forgiveness. Taking down the image. I am going to ask the photographer to take down the image. And I beg for your forgiveness. I went too far, I made a mistake, and I was wrong."
The image caught the attention of the Secret Service. Initially, the agency did not cite the image in any of its tweets, but in response to Twitter users sending the image to its account, the Secret Service tweeted Tuesday afternoon, "On it! @SecretService has a robust protective intelligence division that monitors open source reporting & social media to evaluate threats."
An hour later, the agency tweeted, "Threats made against @SecretService protectees receive the highest priority of all of our investigations. #ProtectionNeverRests."
Later in the evening, the Secret Service issued a statement — which did not cite the controversy — saying, "The U.S. Secret Service has a critical mission. It is always unfortunate when people make statements that could be perceived as threats. We don't have the luxury of knowing a person's intent. Each alleged or perceived threat has to be investigated thoroughly, which taxes Secret Service manpower and resources that could be utilized elsewhere."
The image did not sit well with Donald Trump Jr., who tweeted, "Disgusting but not surprising. This is the left today. They consider this acceptable. Imagine a conservative did this to Obama as POTUS?"
Condemnation of the image was widespread.
"This is vile and wrong," she tweeted. "It is never funny to joke about killing a president."
Hollywood celebs also took to Twitter to criticize Griffin.
Even Anderson Cooper, who is friends with Griffin and hosts CNN's New Year's Eve special with her, tweeted, "For the record, I am appalled by the photo shoot Kathy Griffin took part in. It is clearly disgusting and completely inappropriate."
And a CNN spokesperson added, "We found what she did disgusting and offensive. We are pleased to see she has apologized and asked that the photos be taken down. We are evaluating New Year’s Eve and have made no decisions at this point."
ABC News has reached out to Shields for comment.
ABC News' Christopher Donato and Jack Date contributed to this report.