Before she greeted her cheering supporters at about 11:10 p.m., Chicago Mayor Rahm Emanuel and Secretary of State Jesse White gave her a glowing introduction.
The two-term Chicago clerk told the crowd that she made history as the first Hispanic person to run as a Democrat for a statewide post.
"We really made a big difference in the state of Illinois," Mendoza told the crowd.
WATCH: SUSANA MENDOZA VICTORY SPEECH
Mendoza will serve the remaining two years of the late Judy Barr Topinka's term.
Mendoza also invoked the memory of Topinka, who she called her friend and a "bridge building" who brought people together.
"I really truly do miss her, but I think that she would be proud of what Illinoisans did by sending me to the comptroller's office today," Mendoza said.
WATCH: COMPTROLLER RACE TIGHT UNTIL END
Earlier Tuesday, Mendoza and her family as she cast her ballot at the polling place in Chicago's Portage Park neighborhood.
Munger was appointed to the roll of comptroller after Topinka's death in 2015. State lawmakers subsequently changed the law, essentially forcing Munger into this special election, rather than allowing her to serve the entirety of the comptroller's term.
She voted at Laura B. Sprague School in north suburban Lincolnshire Tuesday morning.
Munger had out-raised her opponent by a significant margin, building her campaign war chest up to a robust $6.8 million.
Mendoza had raised less than half as much. Both candidates have struggled to shake the perceived influence of the most powerful politicians in their respective parties.
Mendoza said she would not be influenced by House Speaker Mike Madigan.
Munger said she has demonstrated she is not indebted to Gov. Bruce Rauner.
Check out Voter's Edge, ABC7's election guide, to find your polling place, preview your ballot and learn more about the candidates running in your community.
WATCH: MENDOZA, MUNGER FACE OFF