"I am very happy that we won the match. In the end, we deservedly won it," Nagelsmann told reporters via a translator in Toronto, describing the win as emotional.
"The boys invested a lot. I'm very happy for the whole team because everyone knew they (were) important. Every player that came into the match (was) important."
Substitute Deniz Undav was Germany's hero on the day, scoring two goals in the second half to erase Ivory Coast's lead and fire Germany into the knockout stage.
"When (the game) opens up he's really great at moving around," Nagelsmann said of Undav, adding that the forward's performance could possibly earn him a start in the team's final group-stage match against Ecuador. "Deniz is someone who does needs to be ready; he can jump in right away."
Nagelsmann said his side did not have enough control at the beginning of the game. He was not satisfied with the first 10 minutes after halftime either, resulting in a triple substitution that proved to be the difference.
"I wanted to move something by bringing them in," the coach said, adding that as the game went on he felt his side took more risks.
While Germany are through to the round of 32, Nagelsmann insisted his team's focus is on their next match against Ecuador.
"We have high ambitions but I think every team that takes part in the World Cup has high ambitions," he said. "It's always important to focus on the next steps."