Mendoza's opponent, Darlene Senger, called her to concede the race about an hour after the polls closed Tuesday night.
Mendoza won a special election for comptroller two years ago. This time, she was re-elected to a full four-year term. But the question now is, will she serve all four years or perhaps run for Chicago mayor?
Mendoza, 46, has won praise for cutting costs and adding transparency to the state's bill-paying process. But she's also been criticized for being less than transparent about her political future.
On Friday, mysteriously leaked video showed Mendoza declaring a run for mayor. The campaign said the video was made in the event she decided to run, and no formal decision has been made.
On Tuesday night, Mendoza took the stage but said nothing about the mayor's race.
WATCH: Susana Mendoza thanks supporters after re-election
"Thank you. Thank you for re-electing me as your truth-telling fiscal watchdog who's not afraid to stand up to the biggest bully in this state, Bruce Rauner," Mendoza said.
Through a spokesperson, Mendoza declined a one-on-one interview Tuesday night. If she is running for mayor, she won't have a lot of time to savor this election night victory. The deadline to file signatures and paperwork is November 26, 20 days from now.