Guardiola left Bayern for City after the 2015-16 campaign and made an impressive start to life at the Premier League side.
Several high-profile defeats then led to criticism of the 46-year-old, but Robben does not expect his former boss to fail in Manchester.
"I am not worried about Pep at all," Robben told The Independent.
"I know his philosophy. I know the way he thinks about football and I also know the Premier League, as I have played there for three years, so I know, with all the teams that are in it, it is very, very difficult.
"Every game is a new battle but what I can see - I have not seen a lot because it is difficult to see a lot of games because we are playing all the time - but the thing I have seen a little bit, you can already see his handwriting… and that is for me something that is very positive.
"You do not [generally] see that so quickly, that you can see the handwriting of the coach and the way they are playing… I do not know [if it is] better but maybe [it is] more attractive than it was before and that is what I say.
"He loves the game, he loves football, he loves attacking football. He wants to have the ball, he wants to play and to me, for players, it is also the best. You want to play football. So, yeah, for me, no negative word about it because I love working with him for the last three years."
City have climbed to second place in the Premier League table following their 2-0 win over Bournemouth on Monday, trailing leaders Chelsea by eight points.