The Harry Potter star received her bachelor's degree in English literature from the prestigious Brown University in Rhode Island.
She tweeted a photo of herself in a cap and gown as she prepared to join 2,000 fellow students collecting their qualifications at the Ivy League institution.
The 24-year-old started at Brown in 2009 after saying she hoped the broad curriculum offered by US universities would help make up for lessons she missed while making the Potter films.
When she was at school Watson scored a clean sweep of As in her GCSE and A-level exams.
In an interview earlier this year she revealed how much she enjoyed being away from the public gaze in America.
"For a while it was amazing, as the American press afforded me so much privacy," she told one interviewer following her success in the hit films based on JK Rowling's novels.
However, she recalled there were moments when her fellow students were starstruck.
"On the first day I walked into the canteen and everyone went completely silent and turned around to look at me," she said.
"I had to say to myself, 'It's OK, you can do this. ."
Fans quickly sent goodwill messages on the micro-blogging site, with one named evil_dumbledore after the Potter creation writing: "It's been a long time coming but Emma's day is finally here. In the words of Emma herself, "!" Enjoy your day,"
The official Harry Potter film site tweeted: Congratulations, Emma! We couldn't be more proud!"
She announced in March 2011 that she was taking a break from student life to focus on her film career.
In October of that year she enrolled at Oxford University as a visiting student to read English at Worcester College.
She continued to rack up film credits during her time as a student, including both parts of Harry Potter and the Deathly Hallows, The Perks of Being a Wallflower, This is the End and Noah.