The TTC Board has announced Deputy CEO Bruce Macgregor will take over as the acting CEO to replace Rick Leary.
MacGregor joined the transit agency last October after being the Chief Administrative Officer of York Region for 16 years.
Leary will be stepping down as CEO on Friday after nearly seven years.
Leary, who worked as a Boston transit executive and for the Region of York, joined the TTC more than 10 years ago after being recruited by former CEO Andy Byford.
Recruitment to fill the role on a permanent basis is still ongoing. MacGregor will begin his role on Friday.
The TTC recently announced another wave of enhancements to bus services across the city. In outgoing interviews, Leary has also highlighted the major funding needed to upgrade TTC infrastructure, particularly of Line 2 which is expected to be the biggest hurdle for the new CEO.