The Scottish champions surprised many by progressing to the Round of 16 of Europe's premier club competition with a second-place finish in a group which consisted of Catalan giants Barcelona, Russia's Spartak Moscow and Portugal's Benfica.
Hamann says it is no fluke that Celtic find themselves in the first knockout phase and admits it is a nice change to see a less-fancied team rise against the odds.
"Celtic's qualification to this stage was an amazing achievement," he told the Daily Record.
"In the past, we have seen clubs such as Basel and Cluj get to this stage but they have come from groups where the top team were strong favourites and the next three were all of a similar level.
"But Celtic? They got through at the expense of seasoned campaigners.
"Benfica and Spartak have been in the last 16 for a number of years and have reached quarter-finals so it's been some effort and they have impressed me.
"If I am honest I was delighted to see it because it is refreshing.
"I looked at my old club City's attempts in their group and it was shambolic so to see a team with limited resources playing in not the most competitive league go on and do well is what football is all about."