The three-time champions play their opening match of the tournament this evening (Monday) when they face Portugal in Group G.
"We weren't always available, but we were constantly attached to the national side. We all came together in the final few training sessions and the most important thing is that the German team which plays will be 100% fit," Neuer told FIFA.com.
"I feel well and fit. I have no limitations whatsoever and I have trained fully; I feel upbeat."
Germany reached the semi-finals of the 2010 World Cup in South Africa before losing to eventual champions Spain.