His best finish at the Ski Jumping World Championships is fifth in the normal hill team competition in Oberstdorf on 20 February 2005, while his best individual finish is seventh in the large hill competition in Sapporo on 24 February 2007.

In the Ski Flying World Championships, his best finish is seventh in the team competitions in 2004 and 2006.

On 15 February 2015 in Vikersund, Vassiliev flew to a distance of 254 m (833 ft) but crashed hard onto near-flat ground.

[1] On 15 October 2016, Vassiliev jumped 147.5 m (484 ft) in Sochi at the Russian National Championships, improving the five-year-old summer world record on a plastic surface.

In 2001, during the Four Hills Tournament, Vassiliev tested positive for the substance Furosemide, which is a banned diuretic.