The Black Stars are set to take on the Carthage Eagles at the Ismailia Stadium in continuation of a quest to win the continental championship for the first time since 1982.
With hosts Egypt and Cameroon, the two most successful teams in the history of Afcon, seeing their title dreams ended on Saturday, Ghana - the third most successful nation - have been given just enough of a heads-up.
"Right from day one, I said you can never underrate any team but I have total confidence in my players," Appiah said at the pre-match press conference on Sunday.
"They [Black Stars] are good and we are motivated going into the game tomorrow.
"Tunisia have a good team and no one should underrate them, we just have to make sure we put up our best to win the game.
"The most important thing is we take each game as it comes, the fact that Egypt and Cameroon are out should tell you what is happening."
Monday's match will be the eighth meeting between Ghana and Tunisia at Afcon.
With six wins and a draw in favour of the Black Stars, the Carthage Eagles are the team the West Africans have played most without losing against at the continental showpiece.
"In football nowadays, you don't have to rely on past achievement so if we have had the upper hand over Tunisia doesn't mean it is going to be easy," Appiah remarked.
"We just have to prepare well for them and forget about the past.
"I think tomorrow's game will be entertaining - both teams are very strong.
"I have always said I have total respect for every team in this competition and I think Tunisia are not a team that we can walk over them."
The winners of the match will face one of debutants Madagascar or Democratic Republic Congo in the quarterfinals.