But they found that a Holocaust-denying cartoon in a separate case was punishable.
The prosecution service had received complaints about Wilders reproducing controversial Danish cartoons of the prophet on his website, as well as their display on a television programme.
It had also received complaints about two cartoons published on the website of the Arab-European League (AEL) lobby group, one of which allegedly shows Jews denying that the Nazi Holocaust happened.
The Danish cartoons and their reproduction were not punishable, the prosecution service said in a statement.
"The cartoons are about the Prophet Mohamed, but don't say anything about Muslims. None of the cartoons are offensive towards Muslims or contribute to hatred, discrimination or violence against Muslims."
The Holocaust cartoon "is punishable because it offends Jews on the basis of their race and/or religion."
The AEL has agreed to remove the cartoon from its Dutch website, said the statement. "If it complies, charges will be provisionally dropped."
The Mohammed cartoons originally appeared in Danish newspapers in September 2005, sparking protests across the Muslim world. Five people died in Pakistan in protests in February 2006.
In a separate investigation, Wilders faces prosecution for inciting hatred against Muslims by making statements comparing Islam to Nazism.
He made a 17-minute film, Fitna, which UN Secretary General Ban Ki-moon has called "offensively anti-Islamic". The screening of the film last year prompted also protests in Muslim nations.
Source: Sydney Morning Herald