At the ICF Canoe Sprint World Championships, Opalev has won 20 medals between 1997 and 2007. This includes eleven golds (C-1 200 m: 1999, 2002, 2003; C-1 500 m: 1998, 1999, 2001, 2002, 2006; C-1 1000 m: 1999, C-4 200 m: 2002, 2005), six silvers (C-1 200 m: 2001, 2005, 2007; C-1 500 m: 2003, C-1 1000 m: 2002, C-4 1000 m: 1997), and three bronzes (C-1 500 m: 2005, C-1 1000 m: 2003, C-4 200 m: 2001). Opalev also won two more medals at the 2003 world championships in Gainesville, Georgia, United States with golds in the C-4 200 m and C-4 500 m events, but were stripped of those medals when teammate Sergey Ulegin failed a doping test.