Elan Musk with to independent board chairman if the motion had not been defeated, a regulatory filing on Thursday.
BlackRock-managed funds voted for a measure the board chair of an independent director, according to a Black Rock filing with the U.S. Securities and Exchange Commission.
More than 86 million shares voted against the proposal at a June meeting, less than 17 million votes in favor, according to Tesla.
Musk serves both as Tesla's chairman and chief executive officer. Some corporate-governance activists call for the split between two people to improve oversight, and the new filing revealed at least one major investor backed search changes at Tesla. BlackRock's role in the proposal is not previously reported.
Musk has been given public pressure on the company's spending and after tweeting on Aug. 7.
Tesla's board had said that the company's success Musk's "day-to-day exposure to the company's business."
Yet top proxy adviser Institutional Shareholder Services supports the proposal, citing concerns about Musk's pay and board independence.
"BlackRock's approach to investment stewardship is driven by our fiduciary duties to our clients, the asset owners," a BlackRock spokeswoman said in an emailed statement. "Our approach to engaging with and proxy voting activities is consistent with our commitment to drive long term shareholder value for our clients."
Blackrock funds are a top 10 Tesla stockholders, accounting for nearly 6.5 million of Tesla's 170 million shares, according to Thomson's Reuters data based on public filings.
Vanguard Group Inc-run funds voted against the independent chair proposal, a recent filing showed. Funds run by Fidelity Investments sided with Tesla on director votes and other controversial items.
BlackRock's filings thus appeared in favor of shareholder proposals at Facebook Inc. Incorporated.
Some companies are structured in a way that effectively gives some shareholders more power than others, regardless of the number of shares they hold.
Netflix, including an advisory vote on executive pay.
(Reporting by Trevor Hunnicutt; Additional reporting by Ross Kerber; Editing by Cynthia Osterman)