Billionaire Elon Musk said the unnamed staff member tried to bring down Tesla after being refused a promotion.
The disgruntled employee is said to change the code of Tesla’s IT systems and sent sensitive data to unnamed third parties.
Mr Musk made the dramatic claims in an email to staff after a fire disrupted work at Tesla’s factory in Fremont, California.
The 46-year-old CEO said the factory had to stop production for several hours following the blaze on Sunday.
Mr Musk said the “strange incident” at the California plant was “hard to explain”, suggesting foul play was responsible.
He wrote to staff, in an email seen by Reuters: “Could just be a random event, but as former Intel CEO Andy Grove said, ‘Only the paranoid survive’.
“Please be on the alert for anything that’s not in the best interests of our company.”
In a separate email, the mogul revealed he had discovered a saboteur in the company’s ranks.
He said he was “dismayed” to learn that a Tesla worker had “conducted quite extensive and damaging sabotage”.
Mr Musk added: “The full extent of his actions are not yet clear, but what he has admitted to so far is pretty bad.
“His stated motivation is that he wanted a promotion that he did not receive.
“In light of these actions, not promoting him was definitely the right move.”
The inventor said Tesla would investigative if the employee was acting alone or in collaboration with “any outside organisations”.
He warned: “There are a long list of organisations that want Tesla to die.
“These include Wall Street short-sellers, who have already lost billions of dollars and stand to lose a lot more.
“Then there are the oil and gas companies, the wealthiest industries in the world – they don’t love the idea of Tesla advancing the progress of solar power and electric cars.
“Don’t want to blow your mind, but rumour has it that those companies are sometimes not super nice.
“Then there are the multitude of big gas/diesel car company competitors.
“If they’re willing to cheat so much about emissions, maybe they’re willing to cheat in other ways?”