Janet deCoux was born on October 5, 1904 in Niles, Michigan, the youngest of the five children of Bertha Wright deCoux and Rev. Charles John deCoux, an Episcopal clergyman. The family moved to Grand Rapids in 1908 and four years later to a farm in Gibsonia, outside Pittsburgh, Pennsylvania.
deCoux studied with Joseph Bailey Ellis at the Carnegie Institute of Technology from 1925 to 1927. She then apprenticed in the New York studio of C. Paul Jennewein for fifteen months, followed by a year at the Gorham Bronze Division learning architectural modeling. She also worked with Aristide Cianfarani in Providence, and for Alvin Meyer in Chicago. While serving her apprenticeships, she attended night school at the New York School of Industrial Arts, the Rhode Island School of Design, and the Art Institute of Chicago. deCoux was then employed in James Earle Fraser's studio where she had previously assisted Gozo Kawamura.
In 1932 deCoux met Eliza Miller in the sculpture department of Carnegie Tech, beginning a sixty-year relationship in which they shared a shop and adjoining studios in Gibsonia, Pennsylvania. For several months in 1935, deCoux traveled to Germany, Italy, and Switzerland, where she joined her friend Aly Moore, the wife of sculptor Bruce Moore. She first met longtime friend Father Hughson on a ship returning to the United States from Europe.
A Guggenheim Fellowship awarded to deCoux in 1938 was renewed for a second year. In 1943, she became resident instructor at Cranbrook Academy of Art.
Janet deCoux died in December 1999.