A combination of births and immigration currently makes for a growth rate of 20,000 to 25,000 new inhabitants each year, according to Himpele Klemens, head of the statistics department of Vienna's city government.
During the past 14 years, Vienna's population has grown by 250,000 new residents – roughly the same as the number of people who live Austria's second largest city, Graz.
"We are currently experiencing an absolute growth phase," Himpele told the Austrian Press Agency (APA).
Vienna is the second-largest city in the German-speaking world, sitting behind Berlin with its 3.5 million people.
In 1934, Vienna had 1,940,000 inhabitants, down from two million in 1910. The impact of two world wars left the former capital of the Austrian-Hungarian empire at only 1.62 million people in 1961, and subsequent years of decline in the birth rate meant that the city had only 1.48 million people in 1987.
The population growth has only been occurring since 2004, with more people being born than dying in Austria's capital city. Currently, it is estimated there are around 19,500 births and around 16,000 deaths each year.
By 2050, statisticians expect the average life expectancy in Vienna to be 89 years for women and 85 years for men. Currently, 51.7 percent of the city's population is female.
Despite the increasing number of elderly people, the average age of Viennese is falling – by 2016, Vienna will be the youngest place in Austria, with 14.2 percent of the city's residents under 15 years old.