Greg Carter will remain with the business in an advisory role.
Carter, who co-founded the business in 2014, is to remain with Growth Street in an advisory role, the company said.
Growth Street did not reveal details why Carter had stood down from the role.
Growth Street is now on the hunt for a replacement CEO.
It did not give a timeline on when it hoped to recruit a replacement by.
Carter's day-to-day responsibilities will be assumed by Kim Goetzke, Growth Street's Operations Director, who has been promoted to Chief Operating Officer and will assume many of Carter's day-to-day responsibilities.
Carter's other responsibilities will be assumed by other members of Growth Street's management team.
The exit of Carter follows Growth Street making a number of redundancies last month, after it axed its "hybrid" business model and shifted to a digital-focused approach.
The job cuts follow Growth Street contacting its lenders telling them that two loans, valued at more than £1m, had defaulted.
The London-based peer-to-peer lender said it had told investors that the cost of the two defaults would be registered on the company's balance sheet.
It said this was "to protect investors from being exposed to losses from these two facilities, and to allow Growth Street the time and flexibility to maximise recovery".