Barosaurus was named by Marsh (1890).

It was synonymized subjectively with Amphicoelias by Galiano and Albersdörfer (2010).

It was assigned to Sauropoda by Marsh (1890), Huene (1908) and Huene (1909); to Morosauridae by Huene (1927), Huene (1927) and Huene (1929); to Cetiosauridae by Lull (1924) and Tatarinov (1964); to Titanosauridae by Romer (1966); to Atlantosauridae by Marsh (1895), Marsh (1896), Marsh (1897), Nopcsa (1901), Hay (1902), von Zittel (1911) and Charig (1967); to Brachiosauridae by Madsen and Miller (1979); to Diplodocidae by Zittel (1890), Marsh (1898), Nopcsa (1928), Hay (1930), Galton (1977), Berman and McIntosh (1978), Charig (1980), McIntosh (1981), Russell (1984), Bonaparte (1986), Bonaparte (1986), Carroll (1988), Miller et al. (1991), Salgado (1993), Britt and Naylor (1994), Upchurch (1995), Upchurch (1995), Calvo and Salgado (1995), Wilson and Smith (1996), McIntosh (1997), Dodson (1997), Sereno (1997), Wilson and Sereno (1998), Wedel et al. (2000), Upchurch et al. (2004), Harris and Dodson (2004), McIntosh (2005), Gallina and Apesteguía (2005), Rauhut et al. (2005), Chure et al. (2006), Suteethorn et al. (2010), Ksepka and Norell (2010), Whitlock (2011), Ibiricu et al. (2012) and Mocho et al. (2014); to Diplodocinae by Tschopp et al. (2015); to Diplodocoidea by Xing et al. (2015); and to Diplodocinae by Romer (1956), Steel (1970), Swinton (1970), Coombs and Molnar (1981), McIntosh (1990), Curtice (1995), Salgado (1999), Wilson (2002), Salgado et al. (2006), Remes (2006), Royo-Torres et al. (2007), Ruiz-Omeñaca et al. (2008), Mannion et al. (2012), Tschopp and Mateus (2013), Foster and Peterson (2016) and Melstrom et al. (2016).