Although a relatively minor figure to emerge from nearly two centuries of an intricate history of French activism, Flora Tristan (1803-44) is an original thinker noteworthy for her outstanding synthesis of feminism and socialism that still has resonance. For scholars and activists alike, Jules-Louis Puech has been an indispensable source. This article looks at how Puech gained his expertise: he deserves more recognition for his life's work that encapsulates the diversity, richness, and tensions of socialism and feminism in French history. By contextualizing Puech's 1925 biography of Flora Tristan using hitherto overlooked evidence, this article will offer new insights into socialist interpretations of her and a better understanding of the workings of past generations of academics and activists in French labour history. Puech's biography contains unique awareness of a complex relationship of feminism and socialism in labour history in the first half of the twentieth century: a vexed question that remains problematic to this day. A closer look at Puech is long overdue and vital for the advance of our knowledge of both Flora Tristan and Puech because he is of equal interest as a historical figure and actor in a neglected aspect of the historiography of reformist socialism.