Guardiola’s side strolled to a routine 2-0 win against the Bundesliga outfit, securing a 4-0 victory on aggregate to cruise into the last-eight.
Kevin De Bruyne opened the scoring with a fierce drive from outside the area before Gundogan doubled the lead six minutes later.
Latching onto a neat ball from the impressive Phil Foden, Gundogan took one touch to control and another to push the ball past the onrushing Monchengladbach goalkeeper Yann Sommer.
City never looked in danger of losing control of the tie and they joined Real Madrid, Liverpool, Paris Saint-Germain, Borussia Dortmund and Porto in the quarter-finals line-up.
It was Gundogan’s 15th goal for Manchester City this season in all competitions and Guardiola was left ‘delighted’ with the Germany international’s latest contribution.
‘He’s always had a sense of goal, playing in Dortmund,’ Guardiola said in a post-match interview.
‘He’s an incredibly nice guy. He’s one of the… I will never forget the time we spent together.
‘As a player he is one of the most intelligent, wiser players I have ever trained, I have ever seen.
‘So delighted with the performance from Ilkay again and from all of the team.’