Cannon made a short statement outside the federal courthouse after giving brief answers inside to a judge's questions. He entered a plea of guilty to one count of honest services fraud.
"Much has been given to me in the way of the public's trust. I regret having acted in ways that broke that trust," Cannon said. "I love Charlotte. It is the city of my birth. I regret having hurt the city that I love."
Cannon asked his former constituents to forgive him.
When he was first elected to the city council in 1993, Cannon, then 28, was the youngest councilman in Charlotte's history. He was elected mayor in November.
On March 26, less than four months after taking office, Cannon was arrested and resigned. Federal prosecutors said he took bribes from FBI agents posing as developers.
Cannon faces up to 20 years in prison, although the actual sentence is likely to be much shorter. He has agreed to cooperate with the ongoing investigation.