Scholars have paid significant attention to the role of gender in social movements, especially in the women’s health and other feminist protest organizations. Gender issues have been less studied in other social movements, such as the anti-nuclear movement, and when they have, then almost always with a focus on the role of women. This paper explores the role of men and the performance of masculinities in protests against civilian nuclear energy. During the 1970s-1990s, activists performed three distinct forms of protest (sabotage, counter-information, and counter-expertise) in dissent against Superphénix, an experimental nuclear reactor built in Creys-Malville, France. This paper looks at how these different forms of protest were grounded in traditional Western views of masculinity, especially virility and paternalism. By comparing and contrasting counter-expertise in the anti-nuclear and the women’s health movement, the paper argues that anti-nuclear counter-expertise was less about providing an alternative view of nature, than personally discrediting official experts in a fight of “man against man” (Lewontin 1968, 2). Finally, it reflects on the consequences of these types of confrontational masculinity on the possibility of science-based dissent.