The layoffs will be announced in the coming weeks, according to unnamed sources who spoke to Bloomberg News and the Wall Street Journal.
A memo from BlackRock's president Rob Kapito and chief operating officer Rob Goldstein said the job cuts have not been finalised.
BlackRock declined to comment.
The last time BlackRock cut a significant number of jobs was in 2013 but the firm ended the year with a higher headcount.
The new round of layoffs comes following months of volatility in the financial markets, which has negatively impacted the income made by traditional banks and other investment houses.
Rivals like Franklin Resources, AllianceBernstein and State Street are also shedding jobs as part of their cost-cutting efforts.
BlackRock has 13,000 employees globally and manages around $4.6tn in assets.

In July, Michael Gove raised the possibility of early release for those who gained skills and qualifications.
Led by head teacher Dame Sally Coates, the inquiry will report early in 2016.
It will also consider the greater use of technology and the "direct engagement" of employers in shaping prisoners' learning.
Prison Reform Trust director Juliet Lyon said: "Providing people with the knowledge and skills to help them lead a law-abiding life on release should be a central aim of a modern and effective penal system."
Mr Gove said: "We have more than 80,000 adults in our custody.
"One of the most important things we can do once they are inside the prison walls is to make sure that they get the literacy and numeracy skills they need to make them employable and positive contributors to society once released.
"For those serving longer sentences, education and training is a key part of their rehabilitation.
"We must have the right incentives for prisoners to learn and for prison staff to make sure that education is properly prioritised.
"I want to see prisoners motivated to engage in their own learning, and governors with the right tools to be more demanding and creative about the education provided in the prisons they run.
"I have seen some excellent examples of innovation and visionary organisations providing prisoners with education opportunities and qualifications they actually need to help secure a job on release. But I want to see more."
In a speech in July to the Prisoner Learning Alliance, Mr Gove called for an end to the "idleness and futility" of prison life.
He said the inability of prisoners to read properly or master basic mathematics made them prime candidates for reoffending.
A system of "earned release" would be a major change from the current policy where most prisoners are automatically released on licence half way through their sentences.
In July, Mr Gove said he recognised "technical and complex policy questions" about how such a change could be implemented.
The world's largest money manager BlackRock reportedly plans to cut 400 jobs, or about 3% of its workforce, in its biggest round of layoffs to date.
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The justice secretary has ordered a review to consider the "incentivisation of prisoners to participate in, attend and achieve at education".