A Rothschild & Co spokesperson confirmed the change, which takes effect on Oct. 1.
With Bossart, the French investment bank wants to expand its market share in Switzerland.
Bossart headed JP Morgan's investment banking in Switzerland for 10 years and was also country head since 2014. During this time, he made JP Morgan the third-largest investment bank in Switzerland after Credit Suisse and UBS.
He was instrumental in a series of big transactions such as ChemChina's $46 billion takeover of agrochemical group Syngenta, DSV's purchase of logistics company Panalpina, and the U.S. IPO of sports shoe manufacturer On Running.
Before joining JP Morgan, he worked at Deutsche Bank and UBS. JP Morgan had said in July that Bossart was leaving and would be replaced by Reinout Böttcher.
One of the sources said he wanted to return to working more on deals and advising firms rather than spending much of his time on management.
Rothschild & Co, controlled by the founding family, generates two-thirds of its income with transaction advisory services and the rest with other services including managing assets for wealthy private clients and professional investors. Unlike the big banks, Rothschild & Co does not offer financing through its own balance sheet or high-yield bonds. This limits its revenue streams but also makes it easier to provide independent advice to corporate clients. It has a strong position especially in mid-sized deals.
One source said Bossart wants to move more into the business of advising on financing and restructuring in addition to its main business of advising on takeovers and IPOs, and to increase the number of employees from around 10 now.
The current head of the Swiss advisory business, Gian Reto Conrad, with whom Bossart started his career at UBS, will remain at Rothschild & Co.
(Reporting by Oliver Hirt, writing by Michael Shields; Editing by Silke Koltrowitz)
By Oliver Hirt