The Arsenal defender recently returned to training after three months on the sidelines with injury and feels he is ready to fight for his place in the national team
The centre-back returned to training this week after spending the past few months on the sidelines with an ankle injury, and looks set to be ready in time to feature for Joachim Low in next month's tournament.
And the Arsenal man is positive of securing a starting berth in Germany's Group B opener against Portugal on June 9.
"I'm very confident over the Euro preparations," Mertesacker told Kicker magazine.
"Right now, everyone is trying to gain a good foundation and reach a good level. And then there is the decision of the national team coach to say who his favourites are.
"With Holger Badstuber and Mats Hummels, we have two young players who have sparked a struggle for spots in central defence again."
"[However], I've always felt a certain confidence because I have almost always played [for Germany]."
The 27-year-old added that the Nationalelf were in excellent shape heading into Euro 2012 as the team look to capitalise on their sensational qualifying campaign which saw them win all 10 games played.
"The team is ultimately only as good as the results that it has achieved," he noted. "But it's clear that the conditions are the best we've ever had."