Her departure has been planned for a few months and precedes the recent drama surrounding CEO Elon Musk's aborted attempt to take the electric carmaker private. Her last day will be Sept. 7.
"We'd like to thank Sarah for all her contributions to Tesla and we wish her the best," said a Tesla spokesperson in an emailed statement. "Sarah's transition has been underway for a couple of months and Dave Arnold, Tesla's Sr. Director of Global Communications, will take on her responsibilities."
The top communications job is vital to Tesla because, unlike other automakers, the Palo Alto, California-based company doesn't spend heavily on traditional advertising and relies on its customers to spread the word about its products.
It is also an exhausting one, as the company receives an enormous amount of attention from the automotive, financial, technology and mainstream press. Musk himself is the public face and voice of the company, and often communicates directly via Twitter, where he has more than 22 million followers.
"Historically, we have been able to generate significant media coverage of our company and our vehicles, and we believe we will continue to do so," Tesla said in its most recent 10-K. "To date, for vehicle sales, media coverage and word of mouth have been the primary drivers of our sales leads and have helped us achieve sales without traditional advertising and at relatively low marketing costs."
O'Brien joined Tesla in 2016 from Apple.