The figure equates to more than 1.5 billion people.
Covid-19 has infected more than 3.1 million people around the world and killed nearly 220,000.
The ILO says those with informal work arrangements are most in danger – many are in the retail sector, manufacturing and food services industry.
Already, two billion informal workers have seen their wages fall by a global average of 60% during the first month that the pandemic unfolded in their region.
“For millions of workers, no income means no food, no security and no future. Millions of businesses around the world are barely breathing,” said ILO Director-General Guy Ryder.
“They have no savings or access to credit. These are the real faces of the world of work. If we don’t help them now, they will simply perish,” he added.