Uber is being sued for stealing trade secrets and technology from Google.
Waymo, set up by Google owner Alphabet, is taking legal action against Otto, Uber's self-driving vehicle unit that it bought last year for $700m.
The lawsuit argues that former Waymo manager Anthony Levandowski took information when he left to co-found a venture that became Otto.
Uber said it took the allegations seriously and would review the matter carefully.
The lawsuit alleges that Mr Levandowski "downloading 14,000 highly confidential and proprietary design files" during his time as a Google employee.
"We believe these actions were part of a concerted plan to steal Waymo's trade secrets and intellectual property," Waymo said.
Alphabet created Waymo earlier this year as a way of bringing self-driving technology - which Google has been working on for years - to market.
In a blog post detailing the action, Waymo said it was a difficult move to bring the legal action.
"Our parent company Alphabet has long worked with Uber in many areas, and we didn't make this decision lightly," the blog said.
"However, given the overwhelming facts that our technology has been stolen, we have no choice but to defend our investment and development of this unique technology."
The technology in question is LiDAR, a laser-based radar system that helps the self-driving cars "see" what is around them.
In court documents filed on Thursday, Waymo alleges one of its employees was recently copied in to an email intended for Otto's staff. Attached to the email were said to be machine drawings of Otto's LiDAR circuit board.
"Its design bore a striking resemblance to Waymo's unique LiDAR design," Waymo said.
"We found that six weeks before his resignation this former employee, Anthony Levandowski, downloaded over 14,000 highly confidential and proprietary design files for Waymo's various hardware systems, including designs of Waymo's LiDAR and circuit board.
"To gain access to Waymo's design server, Mr Levandowski searched for and installed specialised software onto his company-issued laptop. Once inside, he downloaded 9.7 GB of Waymo's highly confidential files and trade secrets, including blueprints, design files and testing documentation.
"Then he connected an external drive to the laptop. Mr Levandowski then wiped and reformatted the laptop in an attempt to erase forensic fingerprints."