Russia are favourites to top the group and they completed their preparations for the tournament with an impressive 3-0 win over Italy.
Having reached the semi-finals four years ago, hopes are high that a similar squad can reach the same lofty heights.
And Advocaat believes his group deserve to be considered dark horses for success in Poland and Ukraine.
“We have a good team, we have the quality, and it is very important that the players start believing in that,” he told uefa.com.
“So, yes, if we have the form and everything is going the right way, we have a very dangerous team.”
Goalkeeper IgorAkinfeev, right-back Aleksandr Anyukov and striker Roman Pavlyuchenko are all fit to face the Czechs after coming through training.
Andrey Arshavin has also been in impressive form, and Advocaat admits he feels the 31-year-old benefited from his loan move to Zenit St Petersburg from Arsenal in January.
“He is a crucial player for us, but he still has to improve his game.
“He did not play much at Arsenal, so I was very happy he went back to Zenit and started getting his form back.
“Arshavin is a player of moments — he can score out of nothing, and you don’t have too many of that kind of player in the world.”
Advocaat, who will join PSV Eindhoven after the finals, knows there will be sides more fancied to lift the trophy, but he feels Greece’s 2004 success shows just how open the Euros can be.
He said: “Realistically, Spain, the Netherlands and Germany have the better sides and better individuals.
“But, again, in a tournament like this anything can happen, as Greece showed in 2004. So we are a nice outsider.”
Czech Republic coach Michal Bilekh has injuryconcerns over two of his key players ahead of the clash at the Municipal Stadium in Wroclaw.
Striker Milan Baros, top scorer at the 2004tournament, has been struggling with a muscle injury which has kept him out of training for most of this week.
But Arsenal midfielder Tomas Rosicky is likely to have recovered from a calf injury to feature.