Dozens of religious group members holding candles and incense burners chanted slogans against the movie outside the city lawcourts.
An Athens court will rule on the case Thursday, hours before the film is due to premiere in Greek cinemas.
The powerful Church of Greece has deplored "The Da Vinci Code," which is based on a blockbuster book by Dan Brown, but stopped short of urging its boycott.
A separate group of theologians, lawyers and judges has threatened legal action against movie theaters that screen the film.
Some 90,000 tickets have already been sold for the film, according to state NET television, while police are planning heightened security outside cinemas for fear of rowdy protests by religious groups, the AP reports.
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