The first explicit use of Frege's work appeared in Piaget's writings in 1949, when he was over 50 years old. This cries out for explanation since Piaget was himself the author of texts on logic and epistemology some 25 years before this. My discussion centers on three questions: (1) Did the work of either Frege or Piaget influence the work of the other? (2) Are there any parallels between Frege's and Piaget's positions? (3) Are there any implications of this argument for developmental psychology? My answer to the first question is Yes—Frege did influence Piaget right from the outset. My answer to the second question is Yes—there are at least three striking parallels, namely logic and judgment, number conservation, and sense and meaning. My answer to the third question is Yes—three implications concern nonpsychologism and psycho-logic, psychological laws and the causal origin of human judgment, and developmental epistemology as a linking science between logic and psychology.