The Football Association of Wales (FAW) said they expected around 5700 Scotland fans in the stadium, although an unknown number have also bought tickets for the Welsh end.
The Welsh authorities had put measures in place to stop the practice but Scotland fans have been using English addresses to get their hands on the tickets.
A further 2000 fans are expected to head to Cardiff without tickets and watch the game in pubs.
Defeat for either side would effectively end their World Cup hopes.
The game will be poignant for Scottish fans returning to the city where manager Jock Stein died shortly after Scotland drew with Wales on September 10, 1985, to qualify for the 1986 World Cup.
Ian Gywn Hughes, of the FAW, said he expected a friendly atmosphere in and around the stadium and that no additional security measures had been put in place.
Mr Hughes said: "We anticipate a great atmosphere. There'll be a few thousand Scottish fans without tickets but Cardiff's a great city – we don't have problems in our matches. "
Hamish Husband, a spokesman for the Tartan Army, said Scotland fans had managed to get tickets for the home end.
He said: "The Welsh FA think they are on top of it but there is no animosity among the international fans."