The reductions at the money managing firm would be equal to around three per cent of the firm's total workforce of 13,000 employees.
The cuts will be spread evenly across regions and divisions, and the company will continue to expand roles in other areas of the business, the source said.
Earlier this year, BlackRock chief exec Larry Fink said recent market volatility had the potential to cause job losses at the group.
After a bumpy start to the year for global markets, Fink told CNBC in January: "Having a market decline like this in the first couple of weeks of the year really, in my mind, puts a negativity across the economy."
He added: "I actually believe you're going to start seeing more layoffs in the middle part of the first quarter, definitely the second quarter because of this."
BlackRock has declined to comment.