Addressing supporters, Raoul said he received a call from opponent and former governor Pat Quinn congratulating him on his victory and conceding the race.
He thanked his parents, family and supporters during his victory speech.
The Chicago senator led seven other candidates Tuesday including Quinn. The race became an open seat following the surprise announcement Lisa Madigan would not run for a fifth term.
Raoul outspent competitors and received establishment backing from the Cook County Democratic Party. He touted endorsements from teacher and labor unions, saying he'll represent workers and families.
Raoul took over then-Sen. Barack Obama's seat in 2004.
WATCH: Pat Quinn speaks to supporters
Raoul voted earlier Tuesday at Kozminski Community Academy with his children.
"I think this is what it's about, it's about the next generation. I don't think it's about being stuck in the past. We need to move on from the past populist type of politicking and really roll up our sleeves and work on the issues," Raoul said.
Erika Harold won the Republican nomination. She beat out Garry Grasso, a litigation attorney.
Harold has GOP establishment backing and has received campaign contributions from Republican Gov. Bruce Rauner. Despite those connections, she has positioned herself as a "reform-minded, political outsider" who wants to offer a bipartisan approach to criminal justice reform and other issues.
She also wants to take on what she sees to be a corrupt political machine run by Speaker of the House Michael Madigan, a Chicago Democrat.
"The first person who I actually saw vote for me was my grandmother, who's 96 years old, and she said how proud she was to have lived to see the ability to vote for me. And she's African American and being able to vote this morning and to think about the fact that she was born at a time when voting running for office, running for attorney general would not have even been a possibility makes me really take this moment in," Harold said.
Quinn voted at Galewood Community Church Tuesday morning.
"The attorney general is a lawyer for the people. We've got to make sure we represent everyday people not just the big shots and corporations," Quinn said.
Chicago Park District leader Jesse Ruiz also voted with his son, who is voting for the first time, in Hyde Park.
In addition to those three, there were five other Democratic candidates who had hoped to get their name on the final ballot in November: State Rep. Scott Drury, former chief administrator of Chicago's Civilian Office of Police Accountability Sharon Fairley, attorney Aaron Goldstein, former federal prosecutor Renato Mariotti, and Highland Park Mayor Nancy Rotering.
While the list of Democrats running was long, there were just two Republicans for voters to choose between: DuPage County Board Member and former Burr Ridge mayor Garry Grasso and Erika Harold, a Harvard Law graduate and former Miss America who cast her vote in Urbana.
The Associated Press contributed to this report.