Marshall will replace John Hughes, who will retire at the end of June and enter a 12-month consulting agreement, with the intention that he will re-join the board as a non-executive director in 2015.
Thorn Group is owner of the Radio Rentals and Rentlo chains.
Marshall has been with Thorn Group for seven years, most recently served as COO of Radio Rentals and Rentlo, and prior to that was GM of Radio Rentals and Rentlo.
Thorn chairman, David Carter, said the decision was made after an extensive, international recruitment campaign by Korn Ferry.
“Finalisation of the process came down to three very competent people, including outstanding internal candidates. This clearly shows the quality of our succession planning, which is something we have been developing over several years,” Carter said.
“James brings excellent operational skills and experience to the position as well as an ability to work effectively with all stakeholders of the business. We are proud that after 20 years with the group he has emerged through the ranks and strongly embodies our culture.
“There will be a continuation of our strategy to become a broader based financial services business under James’ stewardship and we look forward to seeing him lead the company through its final stages of transition and return to growth,” Carter said.
“The board would like to thank John Hughes for his invaluable contribution to the group and we look forward to John and James working closely together on the transition.”