The Ukrainian incumbent controlled his outmatched foe from the get-go, with only a solid Wach right from out of nowhere at the end of round five offering any sort of doubt.
Klitschko, though clearly fazed by the shot, recovered between rounds and continued to wear the Pole down, though he was unable to complete a clear knockout or stoppage.
The win by scorecards of 120-107, 120-107 and 119-109 takes Wladimir’s record to 59-3 from 62 fights, handing Wach his first loss in 28.
The dominant champion had minor question marks hanging over his head going into the bout at the O2 World Arena, having lost his famous trainer Emanuel Steward weeks prior, and facing an opponent bigger and taller than he for the first time.
But Klitschko soon eased into his usual command of the ring, showing superior movement and reflexes to leave Wach looking mostly sluggish.
The contest resembled more of an exhibition than a world title bout after the first four rounds went the Ukrainian’s way, but with seconds remaining in the fifth Wach landed a strong right which left Klitschko’s eyes glazed as he struggled to fend off the approaching challenger for the remainder of the round.
Once he was able to do so, however, Klitschko returned to full control and weakened Wach sufficiently, including leaving a sizeable mark on his right eye. But despite numerous attempts in the championship rounds Wladimir was unable to find the killer combo to cut the fight short.
Nonetheless, after 12 rounds the judges were in no doubt of his successful defence, with just one awarding a solitary round to the Pole, presumably for landing such a shot in round five
"It was a very tough fight and Mariusz had to take a lot of punches," Klitschko said after the win. "I thought that Wach would go down but he fought on."
Klitschko then paid tribute to late coach Steward.
"On July 7 after our last fight we sang happy birthday to him. We miss you, we love you, you are always here in the ring, thank you Emanuel," said Klitschko.