Ketchum will provide press relations services to the group's Information and Communications, Automation and Control, Medical, Power, Transportation and Lighting units.
Patricia Pan, director of Ketchum's Brand Unit will head a team of four, reporting to Siemens' press relations manager Marcia Siqueria.
Ketchum was appointed following a two-month pitch process, involving five other agencies, according to Pan.
Siemens first entered Brazil in 1867, when it built the telegraph line linking Rio de Janeiro and the state of Rio Grande do Sul. It has 7,500 employees and ten factories in the country and reported total revenues of 4 billion reais (US$1.13) last year.