Hasbro, which owns the rights to Scrabble in the US and Canada, sued brothers Rajat and Jayant Agarwalla of India last week for trademark and copyright infringment.
Barry Nagler, Hasbro's general counsel, said: "We view the Scrabulous application as clear and blatant infringement of our Scrabble intellectual property, and we are pursuing this legal action in accordance with the interests of our shareholders, and the integrity of the Scrabble brand."
Facebook forwarded the request to the Agarwalla brothers, who yesterday pulled the plug on the game in the US and Canada until further notice.
The brothers said in a statement: "This is an unfortunate event and not something that we are very pleased about. We will sincerely hope to bring to our fans brighter news in the days to come."
Hasbro's suit comes after the launch of its own official Facebook version of Scrabble for US and Canadian users, which was created by Electronic Arts.
The company said: "We are thrilled that EA has now brought to market a social networking experience that has a genuine Scrabble look and feel."
Toy maker Mattel, which owns the rights to Scrabble outside the US and Canada, also filed a suit against Scrabulous several months ago and is awaiting a decision on its complaint by an Indian court.
In the mean time, Scrabulous players outside the US and Canada can still access the game on Facebook.