Born in 1938, Maria Militza Sion graduated from the Ion Mincu Institute of Architecture in 1961. Upon graduation, she worked at the town of Galati. Retuning to Bucharest in 1966, she found employment at Project Bucuresti Design Institute, were she led the design of multiple residential buildings and, during the 1970s, was a co-author of four cultural centers projects (for the towns of Buzau, Sibiu, Alba-Iulia, and Calan). Between 1978 and 1986, Sion worked on projects for the city of Miercurea Ciuc in Transylvania, designing apartment buildings, a hotel, and a shopping mall. She also acted as a co-author of the Embassy of Romania in Sofia, Bulgaria (1985-1988). While working as an architect, Sion was also a graphic artist: her graphic works received state awards in 1976 (Annual Award for Graphic Art) and in 1981 (Jury for Graphic Art Special Award).

Following the transition to the market economy in the 1990s, Sion opened a private architectural practice in partnership with another female architect, Marina Neagu Sadoveanu. The office worked on hotels and orphanages. 

Sion’s archive is housed at the International Archive of Women in Architecture at Virginia Polytechnic Institute