Huffman entered her plea two months after she was arrested in the investigation named "Operation Varsity Blues", which accused wealthy parents of paying bribes to help their children get into elite universities across the country.
In exchange for her guilty plea, Huffman will serve approximately four months to ten months in prison, for crimes carrying a maximum sentence of twenty years.
Huffman, Lori Loughlin and four dozen other business executives, coaches and more were charged on March 13 with participating in a "large-scale elaborate fraud" to get their children into prestigious universities like Yale, USC, Stanford and UCLA.
Prosecutors said that Huffman allegedly paid Singer's company $15,000 to have a proctor correct the answers on an SAT exam for her daughter, Sophia Grace Macy.
"I didn't want to give the impression the neuropsychologist knew about this", Felicity told the judge while breaking down, NBC News reports. Singer has admitted that he paid "proctors" to correct wrong answers on students' tests or take the exam in their place.
Sentencing was set for September 13. Beyond Huffman Macy's own potential jail time and the fall-out from all that, today's guilty plea must also certainly leave Lori Loughlin and her husband, Mossimo Giannulli, wondering: if those who bow to the feds and take the plea are still facing months of time in federal prison, what might be in store for us?!
"I want to apologize to them and, especially, I want to apologize to the students who work hard every day to get into college, and to their parents who make tremendous sacrifices to support their children and do so honestly", she said. Prosecutors have not explained why. Officials say he bought athletic gear online and worked with a designer to create a bogus photo of his son playing the sport for the application.
Huffman was nominated for an Oscar for best actress for her role in the 2005 film "Transamerica".
Experts differ on the long-term impact the scandal will have on Huffman's career.
Loughlin and Giannulli, who are also charged with money laundering conspiracy, have not publicly commented on the allegations.
A limited series featuring Huffman on the Central Park Five case is expected to debut this month.
The Desperate Housewives actress appeared in court on Monday to officially plead guilty in the case. Seventeen other parents, including Loughlin, have made a decision to fight the charges and formally submitted not guilty pleas.
Singer has pleaded guilty to charges including racketeering conspiracy.