This article adds to the emergent literature on classed fathering by exploring how middle-class and working-class fathers relate to their sons’ ADHD diagnosis. The strong requirement on parents to adhere to a dominant medical discourse of ADHD is used as a case to explore how the entwinement of class and gender shape different fathering practices. The article draws on in-depth interviews with 16 fathers of boys diagnosed with ADHD. These interviews were part of a larger study including interviews with children and their mothers. All the fathers interviewed were critical of the medical understanding of their sons’ behaviour, and seemed, in different ways to defend their sons against the diagnosis and medication. However, this resistance is much clearer in the working-class fathers’ narratives than in the middle-class fathers’. We argue that classed masculinities allow these fathers to take on a love-driven identification with their sons’ problematic masculine behaviour. Seen in a wider context, the fathers’ critical voices offer considerable resistance to the medicalisation discourse, and thus also to currently dominant parenting regimes.