Klitschko secured his 59th win in his boxing career with three defeats. The 36 year-old heavyweight boxer from Kazakhstan, who was adopted by and fought for Germany in recent years, entered the ring facing an opponent who is taller than him for the first time in his career.
Wach was reluctant to engage Klitschko in the early rounds but on the fifth round he came in aggressively and was able to break in to the champion's defenses though he failed to follow through with more attacks as Klitschko regained control.
After the eight round, Wach was wearing off but caught Klitschko with heavy shots towards the end of the round. Klitschko managed to stay and survived the last minute attack.
Klitschko, who towers over his past opponents because of his height and built, stands a little lower than his opponent'
Klitschko won via a unanimous decision, with the judges scoring 120-107, 120-107, 119-109 all in favor of the former Ukrainian fighter.
"It was great to have Rocky here, thank you for your support," said Klitschko
with Hollywood actor Sylvester Stallone ringside in Hamburg to see the fight against Wach, dubbed 'The Viking'.
"He really is 'The Viking' he took a few shots, but kept fighting on, so respect to him."
Klitschko entered the ring without his long-time trainer Emmanuel Steward who passed away last month in his home town of Detroit after surgery for cancer.
"After my last fight in July, we all sang 'Happy Birthday' to Emanuel, but now he is gone and I want to pay tribute to him," added Klitschko.
"He was a great man and we will never forget him."
The former unbeaten challenger Mariusz Wach
from Poland suffered his first defeat in his last 28 professional fights.
"That was the hardest fight of my life, he's a tough fighter," said an emotional Wach, who suffered the first defeat of his career having previously had 15 knock-outs in 27 wins.
"This was the biggest fight of my life and I am just so sorry that I couldn't win it."
Wach's professional record which included 12 knockouts and 17 straight wins
is now tainted with one defeat over a professional career spanning seven years.
The Klitschko-Wach fight has somehow revived the lukewarm attitude of boxing fans on fights being staged in the heavyweight division as more fights are becoming more popular in the lower divisions from welterweight down down to flyweight.