Cho will run for the Progressive Conservatives.
The 76-year-old has represented Scarborough Rouge River on city council for nearly two decades.
In the past he has run unsuccessfully federally for the NDP and has sought a Liberal nomination provincially.
Cho says he will not resign his council seat when an election is called.
An election is expected sometime in the spring, after a new Liberal leader is chosen to replace Premier Dalton McGuinty.