The Saints have several vacancies on their coaching panel next year, due to the impending departures of defensive coach Stephen Silvagni and Sandringham coach Andy Lovell.
Ross Lyon's long-time lieutenant Tony Elshaug also quit the club for personal reasons mid-year but he has returned in a temporary role for the Saints' finals campaign.
Harvey, a veteran of 383 games at St Kilda, joined the Blues in 2009 as a development coach before taking on the role as midfield coach this year.
Lyon, who worked with Harvey in his final two years at St Kilda, said the Saints players will be excited to have the two-time Brownlow medallist back at the club.
“We all look forward to working with him for a number of years to come," Lyon said.
“Working with Robert over his last two years at the club, I was able to understand and appreciate his dedication and passion for the Saints.
“With a brilliant football mind and coaching experience, Robert is sure to add a great amount of depth to our coaching department next year.”
Harvey will be joined in the exodus from Visy Park by defensive coach Brett Montgomery and forward line coach Matthew Lappin.
In a statement released on Monday afternoon, Carlton said Harvey had resigned from his role, while the club had chosen not to renew the contracts of Montgomery and Lappin.
Montgomery started as an assistant under Ratten in late 2007 after ending a 204-game career with Port Adelaide and the Western Bulldogs.
Lappin, a life member at Carlton, has also worked as an assistant to Ratten for the past three seasons, starting as a development coach before taking charge of the forwards.
Carlton football manager Steven Icke thanked the trio for their work and wished them well for their future endeavours.
“We will now seek to find the best possible people to join our coaching panel in what will be the first major changes to our coaching team for two seasons,” he said.
