The first part of the article gives an account of the history and characteristics of the Finnish Tatar minority of approx. 700 people. This group was formed about a hundred years ago when Mishar Tatar-speaking merchants from Tsarist Russia began to settle in Finland. Special emphasis is given to factors explaining the vitality of the Tatar heritage language. The second part describes the compilation and characteristics of the Tatar-Finnish dictionary, which contains both Kazan Tatar and Finnish Tatar vocabulary. The problems encountered in dictionary making are treated as evidence giving insight into the language ecology of the Finnish Tatar language community.