The lawsuit alleges Musk manipulated the price of Tesla shares by issuing materially false and misleading information, according to a copy of the suit which was posted online and confirmed as authentic by the well-known short seller Left.
The suit specifically cites Musk's Aug. 7 tweet about taking Tesla private and claiming that funding for that effort had been "secured." The post sparked weeks of controversy and stock volatility due to questions about funding for his proposal.
Musk reversed course on Aug. 24, when he said in a blog post that the company will remain publicly traded, citing resistance from existing shareholders to his plan to take it private.
One of Left's law firms, Labaton Sucharow, announced the lawsuit in a press release later Thursday.
"This appears to be a textbook case of fraud," Labaton Sucharow partner Michael Canty said in the release. "We believe Musk attempted to manipulate the price of Tesla securities with false and misleading tweets, in a directed effort to harm short-sellers."
Left declined to comment on the lawsuit's details. Tesla did not immediately respond to a request for comment.
Tesla shares closed up slightly Thursday.