Born in Narajów, Galicia, Ukraine, then Austria-Hungary, he emigrated to Montreal in 1911. He worked as a bookkeeper during the day and at night studied art at the Council of Arts and Manufacturers, at the school of the Art Association of Montreal with William Brymner, attended Royal Canadian Academy evening classes with Maurice Cullen and others , and also at the Ecole des Beaux-Arts (1922–1928). From 1928 to 1931, he studied art in Paris with the figure painter Louis Biloul, also sketching at the Académie de la Grande Chaumière and exhibiting his work at the Paris salons. He spent summers sketching in the provinces or visiting museums in Belgium (1928–1931). He returned to Montreal to become a full-time painter.
In 1937, he showed his work in Toronto with the Picture Loan Society. Since then, his work was shown at many galleries in both solo and group exhibitions. In 1996, an 80-piece retrospective exhibited Muhlstock's work at galleries in Québec, as well as in Edmonton.  In 2010, his work was exhibited as part of the McCord Museum's Jewish Painters of Montreal: Witnesses of Their Time, 1930-1948.
In 1978, he was awarded a Doctor of Laws, honoris causa from Concordia University. In 1990, he was made an Officer of the Order of Canada. In 1998, he was made a Knight of the National Order of Quebec.
- Bradfield 1970, p. 327.
- MacDonald 1967, p. 1329.
- "National Gallery of Canada entry".
- McDougall, Anne. "Louis Muhlstock". www.thecanadianencyclopedia.ca. Canadian Encyclopedia. Retrieved 2020-08-05.
- "Jewish Painters of Montreal: Witnesses of Their Time, 1930-1948". Archived from the original on 2014-07-24.
- "Honorary Degree Citation - Louis Muhlstock".
- "Order of Canada citation".
- "National Order of Quebec citation" (in French).
- Bradfield, Helen (1970). Art Gallery of Ontario: the Canadian Collection. Toronto: McGraw Hill. ISBN 0070925046. Retrieved 2020-08-05.
- MacDonald, Colin (1967). A Dictionary of Canadian Artists, vol. 4 (Third ed.). Ottawa: Paperbacks. Retrieved 2020-08-06.