Monaco won his opening match comfortably against Brazilian qualifier Andre Ghem 6-4 6-4 and moves into his second ATP World Tour semi-final of the year - where he will face Guido Pella, who beat top-seeded Janko Tipsarevic in the second round.
Kamke stunned Juan Martin Del Potro Miami back in March and, despite having the backing of the home crowd, struggled throughout as he was beaten in 71 minutes.
"It wasn't easy to play, as it was very cold," said Monaco. "I am happy to have reached the semi-finals and I will have a difficult match against a baseliner tomorrow."
Elsewhere, second seed Tommy Haas, who won the recent ATP Munich before reaching the third round in Rome, retired before his match against Jarkko Nieminen.
ATP Dusseldorf results
6-Jarkko Nieminen (Finland) beat 2-Tommy Haas (Germany) (Haas retired)
Igor Sijsling (Netherlands) beat Jan Hajek (Czech Republic) 6-3 6-1
Guido Pella (Argentina) beat 7-Viktor Troicki (Serbia) 7-6(5) 7-5
3-Juan Monaco (Argentina) beat Tobias Kamke (Germany) 6-3 6-4
ATP Nice results
Gael Monfils (France) beat Robin Haase (Netherlands) 6-2 6-3
Pablo Andujar (Spain) beat 2-Gilles Simon (France) 6-4 7-5
Albert Montanes (Spain) beat Paul-Henri Mathieu (France) 6-4 6-1
Edouard Roger-Vasselin (France) beat 3-Sam Querrey (U.S.) 3-6 7-6(2) 6-1