The Black Stars play their opening match of the tournament against the USA on Monday before facing strong European competition in the form of Portugal and Germany.
While Ghana are expected to struggle in the group, Mensah believes that the team should not be underestimated.
"We have been rated as underdogs in the group, which we are happy about," he told FIFA.com. "For the past four, eight years, we have been written about as underdogs, but we always prove people wrong. But this time we don't know what is going to happen and we're just waiting for the first game.
"We respect that, statistically, the teams in our group are really high-profile, more so than Ghana, and we do respect that. But we're here and we're more focused on our game. And we're here to prove everybody wrong once again."
Mensah will make his 80th senior appearance for Ghana if he is selected to play against the USA.