It is in the foothills of the Serra da Mantiqueira south of the state capital Belo Horizonte at an elevation of , making it one of the ten highest cities in Brazil. Located on the important BR-040 highway (also called Rodovia JK), which links Brasília to Rio de Janeiro, it is from the state capital and Juiz de Fora.
Barbacena has a humid tropical climate with cool summers due to the elevation. Summer averages are and winter averages . The cool climate and abundant rainfall have made Barbacena a center for flower production — the city is the biggest producer of flowers in Minas Gerais, and is nicknamed "City of Roses". Cattle raising and the dairy industry are quite developed and the city is a big producer of milk products; there are also several small textile factories.
Barbacena is also the home of the Preparatory School of Air Cadets (the sixteenth best high school of the country, which belongs to the Brazilian Air Force) and of a Medical School, Faculdade de Medicina de Barbacena (Faculty of Medicine of Barbacena). The city is also famous for the Hospital Colônia de Barbacena, a mental hospital founded in 1903, which was known for its abusive treatment of patients. According to sources, 70% of the patients did not have mental illness, and allegedly 60,000 people died in the hospital. It ceased operations in the mid-1980s. It has been compared to a Nazi concentration camp.
Barbacena was a station on the Estrada de Ferro Oeste de Minas, a narrow gauge railway.