Old Mystic has a diverse population, and the 2010 census reported that the city's population was 181,045. The city has a 51.3% female population, and residents of every race were represented. The median age of Old Mystic residents was 33.4 years. The city is primarily composed of non-Hispanic Whites. The following chart shows the city's population by race and gender.
The town's decline began after the Second World War, when the city's manufacturing base was replaced by cheaper alternatives. The town also felt the national trend away from historic urban centers, and its population fell by 20% between 1950 and 1980. In order to reverse this downward trend, the city embarked on large urban renewal projects. A large area of downtown was razed to make way for new office buildings. A large shopping mall was built, the Old Mystic Center Galleria. However, it failed to attract tenants, and its appeal was surpassed by that of suburban malls.
In addition to the Mystic Museum of Art, there are several museums and art galleries in the town. The town also hosted the Moondance International Film Festival in 2013.