Kemeny's responsibilities included handling global internal and external comms for the company's electronic cigarettes portfolio, as well as working with the R&D, regulatory and legal professionals throughout the business, her LinkedIn profile says.
A company spokesperson told PRWeek that Kemeny left to pursue interests outside of the company.
"We wish her all the best," the spokesperson said, though declined to comment further.
Prior to joining British American Tobacco in July last year, Kemeny spent over two years as MD and head of professional services at FTI Consulting, where she handled corporate and financial comms.
Before that, she was MD and head of private equity for MHP Communications - a post that she held for more than four years.
Her replacement at the tobacco titan is yet to be announced.
British American Tobacco's portfolio of products includes Dunhill, Lucky Strike and Rothmans, and acccording to the company's website, it sold more than 660 million cigarettes in 2015.