Madrid are set to take on the Eredivisie giants in Amsterdam on Wednesday to open their last 16 clash.
Despite their history, Ajax are not one of the tournament favourites due to the club's youth and inexperience at a level this high.
Still, Frenkie de Jong, Matthijs de Ligt and the rest of Erik ten Hag's squad went unbeaten through the group stages, including two draws with Bayern Munich.
Madrid, meanwhile, have enjoyed an upturn in form in recent weeks under Santiago Solari, leading to some speculating that they are again peaking at the right time to challenge fdor continental honours.
And though Kroos insists the Santiago Bernabeu outfit are again ready to go all the way, they are not underestimating any of their opponents.
"It's normal that Ajax will meet us with maximum motivation and we expect it. It will be two tricky games," Kroos told Spox and Goal .
"They have shown against top teams like Bayern how strong and talented they are.
"Luckily, in the last few years we were always fully occupied when it came down to it in the Champions League, regardless of the opponent. Otherwise, we would not have won the title three times in a row. And that's why I'm assuming that, once again, we'll be able to be there.
"Firstly, we are in a good mood after the positive results and secondly there is no reason to underestimate Ajax."
Those results reference a recent run that has seen Madrid climb within six points of Liga leaders Barcelona while also securing a 1-1 draw with their Clasico rivals in the first leg of their Copa del Rey semi-final.
This past weekend, Real saw off local rivals Atletico Madrid 3-1 in La Liga, providing a major confidence boost with the Champions League looming.
"First of all, every single person has come into shape step by step. But you also see that we act more as a team again, work much more closely toegther than in the first half of the season," Kroos said.
"This starts with attacking the opponent. We press much earlier and more aggressively. If you do it defensively as a team, you win many balls.
"The fact that we still have the calmness and the quality in the game with the ball, is currently showing. This is good for everyone. Over such success experiences you win gradually also at mental strength."