He flew aboard Vostok 3 in August 1962, as part of the first simultaneous flight of two spacecraft, with Vostok 4. With Vitali Sevastyanov on Soyuz 9 in June 1970, he set a record (at the time) for the longest space flight of 424 hours and 59 minutes. Nikolayev was selected as a cosmonaut in 1960 and left the programme in 1982.