Nodosaurus was named by Marsh (1889). Its type is Nodosaurus textilis. It is the type genus of Nodosauridae. It was considered monophyletic by Vickaryous et al. (2004).

It was assigned to Ceratopsidae by Depéret (1896); to Stegosauria by Marsh (1889) and Marsh (1899); to Acanthopholididae by Nopcsa (1902); to Omosauridae by Huene (1909); to Stegosauridae by Mansel-Pleydell (1902) and von Zittel (1911); to Ankylosauridae by Nopcsa (1928) and Maleev (1956); to Nodosaurinae by Ford (2000); to Nodosauridae by Marsh (1895), Marsh (1896), Hay (1902), Lull (1921), Russell (1930), Romer (1956), Kuhn (1964), Romer (1966), Swinton (1970), Coombs (1978), Coombs (1978), Molnar (1980), Russell (1984), Tumanova (1987), Carroll (1988), Coombs and Deméré (1996), Carpenter and Kirkland (1998), Carpenter (2001), Blows (2001), Ford and Kirkland (2001) and Garcia and Pereda-Suberbiola (2003); and to Ankylosauria by Vickaryous et al. (2004).