Pylkkänen was a student of Leevi Madetoja and Selim Palmgren, and studied at the Helsinki Conservatory, then in Paris, Rome, and Vienna. He made his breakthrough as a composer with the opera Mare ja hänen poikansa (1943) after Aino Kallas, which was premiered in the Finnish Opera in 1945. It was followed by ten more operas, including the internationally successful Sudenmorsian (1950). From 1960 to 1967 he was artistic director of the Finnish Opera.
In addition to the operas he composed a symphony, a symphonic fantasy, six symphonic poems, a cello concerto, chamber music works, a cantata, film music, a choir cycle for women's voices, songs and two song cycles.