Miina Sillanpää was born during the famine years to peasants Juho and Leena (née Roth) Riktig, who had a total of nine children. She started her work career at the age of 12 at the Forssa cotton factory, and later in the Jokioinen nail factory. At the age of 18 she moved to Porvoo to work as a maid and changed her name from Vilhelmiina Riktig to Miina Sillanpää. From 1900 to 1915 she worked as caretaker of the Helsinki Household Workers' Association's Servants' Home and Employment Agency. Sillanpää worked as inspector of eateries and cafés of Osuusliike Elanto from 1916 to 1932 and as secretary of the Social Democratic Party Working Women's Association from 1932 to 1936.
Sillanpää did not have much of a school education – she had only gone to a visiting school (kiertokoulu) and factory school.
Miina Sillanpää was not a political theoretician, instead she was active in social democratic association activity. She especially campaigned for the rights of working and lonely women (in the 1930s she was intensely active in the Ensikoti activity). She was a member of the party activity group of the Social Democratic Party from 1918 to 1919 and from 1933 to 1940, and also worked as chairwoman of the Social Democratic Women's Association and the Social Democratic Working Women's Association.
Member of parliament
Miina Sillanpää was one of the first nineteen female members of the Parliament of Finland, who were elected in 1907. She served as a member of parliament for a total of 38 years: 1907–1910, 1914, 1917, 1919–1932 and 1936–1947.
Upon election as second Minister of Social Affairs in the Väinö Tanner government of 1926–1927, she became Finland's first female minister.
Sillanpää acted as an official elector of the President of Finland in 1925, 1931, 1937, 1940 and 1943.
Sillanpää was also a journalist. She worked as editor of the Palvelijatar ("female servant") magazine from 1905 to 1906, in the Työläisnainen ("working woman") magazine from 1907 to 1916, and in the Toveritar ("female comrade") magazine from 1922 to 1943.