Citigroup is shuffling the leadership of its wealth management business, whose growth has fallen short of targets during a market downturn that has sapped demand for its services.

Jim O'Donnell, global wealth-management chief, will become a vice-chair of the bank and head of senior client engagement, according to people familiar with the matter, where the longtime markets executive will collaborate with major clients and chief executives. The bank will launch a search for a new wealth-management head, the people said.