This essay sketches the development of a transatlantic network of reformers devoted to solving the problem of juvenile delinquency. It argues that during the middle of the nineteenth century juvenile reform practices spread through a web of newly created reform and social science associations in Europe and the USA. Through these organisations, experts and reformatory administrators developed personal and professional relationships. Child reformers shared papers and publications, and many of them travelled across the Atlantic to attend organisational meetings and tour each other’s institutions. Focusing on the interactions of several key members, this article illuminates the extensive and understudied exchange of ideas that shaped approaches to combating juvenile delinquency on both sides of the Atlantic.