The new policy was shared in emails that were leaked to social media.
Tesla did not respond to a request for comment on the messages, one of which appeared to be addressed to executives.
People who are unwilling to abide by the new rules can "pretend to work somewhere else" Mr Musk said on Twitter, when asked about the policy.
"Everyone at Tesla is required to spend a minimum of 40 hours in the office per week," he wrote in one of the emails. "If you don't show up, we will assume you have resigned."
The emails said staff should report to work at one of the company's main offices, "not a remote branch office unrelated to the job duties".
Mr Musk added that he would personally review any requests for exemptions from the policy.
Mr Musk said working in the office full-time was what the company asks of its factory employees and in-person collaboration was critical to the firm's success.
"There are of course companies that don't require this, but when was the last time they shipped a great new product? It's been a while," he said in an email, one of two that was leaked and shared on social media.
"Tesla has and will create and actually manufacture the most exciting and meaningful products of any company on Earth. This will not happen by phoning it in."
Companies in many industries are wrestling with whether to allow the remote work practices that exploded during the coronavirus pandemic to continue.
Some sectors, such as banking, signalled early on that they would expect staff to return to the office, while others, often in the tech industry, have said they will allow remote work indefinitely. Many places have opted for a mix.