The message, sent on Thursday and titled "pause all hiring worldwide", came two days after the billionaire told staff to return to the workplace or leave, and adds to a growing chorus of warnings from business leaders about the risks of a recession.
Tesla shares fell 9% in US trade on Friday after the Reuters report. The tech-heavy Nasdaq was down about 2%.
In another email to employees on Friday, Musk said Tesla will be reducing its salaried headcount by 10%, as it has become "overstaffed in many areas." But "hourly headcount will increase," he said.
"Note, this does not apply to anyone actually building cars, battery packs or installing solar," Musk wrote in the email seen by Reuters.
Almost 100,000 people were employed at Tesla and its subsidiaries at the end of 2021, its annual SEC filing showed. It did not break down the numbers of salaried and hourly workers.
The Texas-based company was not immediately available for comment.
Musk has warned in recent weeks about the risks of recession, but his email ordering a hiring freeze and staff cuts was the most direct and high-profile message of its kind from the head of an automaker.
"Elon Musk has a uniquely informed insight into the global economy. We believe that a message from him would carry high credibility," Adam Jonas, an analyst Morgan Stanley, said in a report.
US President Joe Biden, asked about Musk's comments on the economy, quipped that he wished Musk "lots of luck" on his "trip to the moon."
Musk, who criticised the Biden administration for "sidelining Tesla & SpaceX," replied on Twitter: "Thanks Mr President!" He included a link referencing NASA's April 2021 award of a $2.9-billion contract to Musk's space company SpaceX to build a spacecraft to bring astronauts to the moon.
So far, demand for Tesla cars and other electric vehicles (EV) has remained strong and many traditional indicators of a downturn - including increasing dealer inventories and incentives in the United States - have not materialised.
But Tesla has struggled to restart production at its Shanghai factory after COVID-19 lockdowns forced costly outages.
"It is always better to introduce austerity measures in good times than in bad times. I see the statements as a forewarning and a precautionary measure," said Hanover-based NordLB analyst Frank Schwope.
Many carmakers achieved record profits in 2021, but the economic situation is now more uncertain, he noted.
Musk's gloomy outlook echoes recent comments from executives including JPMorgan Chase & Co CEO Jamie Dimon and Goldman Sachs President John Waldron.
A "hurricane is right out there down the road coming our way," Dimon said this week.
Inflation in the United States is hovering at 40-year highs and has caused a jump in the cost of living for Americans, while the Federal Reserve faces the difficult task of dampening demand enough to curb inflation while not causing a recession.
Musk, the world's richest man according to Forbes, did not elaborate on the reasons for his "super bad feeling" about the economic outlook in the brief email seen by Reuters.
It was also not immediately clear what implication, if any, Musk's view would have for his $44-billion bid for Twitter. US antitrust regulators cleared the way for the deal on Friday, sending Twitter shares up 2%.
Several analysts have cut price targets for Tesla recently, forecasting lost output at its Shanghai plant, a hub supplying EVs to China and for export.
China accounted for just over a third of Tesla's global deliveries in 2021, according to company disclosures and data released on sales there. On Thursday, Daiwa Capital Markets estimated Tesla had about 32,000 orders awaiting delivery in China, compared to 600,000 vehicles for BYD, its larger EV rival in that market.
'PAUSE ALL HIRING'
Before Musk's warning, Tesla had about 5,000 job postings on LinkedIn from sales in Tokyo and engineers at its new Berlin gigafactory to deep learning scientists in Palo Alto. It had scheduled an online hiring event for Shanghai on June 9 on its WeChat channel.
Musk's demand that staff return to the office has already faced pushback in Germany. And his plan to cut jobs would face resistance in the Netherlands, where Tesla has its European headquarters, a union leader said.
"You can't just fire Dutch workers," said FNV union spokesperson Hans Walthie, adding Tesla would have to negotiate with a labour union on terms for any departures.
In a Tuesday email, Musk had said Tesla employees were required to be in the office for a minimum of 40 hours per week, closing the door on any remote work. "If you don't show up, we will assume you have resigned," he said.
Musk has referred to the risk of a recession repeatedly in recent comments.
Remotely addressing a conference in mid-May in Miami Beach, he said: "I think we are probably in a recession and that recession will get worse."
Other companies have cut jobs or are slowing or pausing hiring amid weakening demand.
Last month, Netflix said it had laid off about 150 people, mostly in the United States, and Peloton said in February it would cut 2,800 jobs. Meta Platforms, Uber and other technology companies have slowed hiring.
In June 2018, Musk said Tesla would cut 9% of its workforce as the then-loss-making company struggled to ramp up the output of Model 3 electric sedans, although its SEC filings showed reductions were more than offset by hiring by year-end.