The public voted Oldman the Best British Film Star for his Academy Award-nominated role as George Smiley in Tinker Tailor Soldier Spy.
The thrilled star said, "This is the first prize for acting in a specific performance that I've received in over 20 years and that makes it all the more special."
Tinker Tailor Soldier Spy was also named British Film of the Year and Best Screenplay at the awards. The latter prize was accepted by Peter Straughan, who created the script with his late wife and writing partner Bridget O'Connor.
Oldman's fellow Oscar nominee Streep was also a big winner, claiming the critics' Best Actress honour for her portrayal of former British Prime Minister Margaret Thatcher in The Iron Lady.
The Artist dominated the RAFA critics' categories, claiming the Film of the Year and Best Filmmaker (Michel Hazanavicius) trophies, while Michael Fassbender was named the critics' Best Actor for his portrayal of a sex addict in Shame.
The full list of winners is:
Critics' Film of the year: The Artist
Critics' Best Filmmaker: Michel Hazanavicius (The Artist)
Critics' Best Screenwriter: Bridget O'Connor and Peter Straughan (Tinker Tailor Soldier Spy)
Critics' Best Actor: Michael Fassbender (Shame)
Critics' Best Actress: Meryl Streep (The Iron Lady)
Critics' Rising Star: Tom Hiddleston
Public's British Film of the Year: Tinker Tailor Soldier Spy
Public's Animated film: Arthur Christmas
Public's Family Film: The Adventures of Tintin: The Secret of the Unicorn
Public's Best British Film Star: Gary Oldman (Tinker Tailor Soldier Spy)
Public's Favourite Film Star: Robert Pattinson
Public's Most Anticipated Film: The Dark Knight Rises.