Shareowners of Monsanto approved the company’s merger with Bayer in the $66bn transaction, which still needs regulatory approval.
Germany-based Bayer agreed in September to acquire the US's Monsanto in an all-cash transaction for $128 per share, which had to be approved by shareholders.
The merged business will bring together Monsanto’s leadership in seeds and traits and Climate Corp platform, which aims to improve farm technology, with Bayer’s broad crop-protection product lines.
The combination also unites both companies’ technology spending, with an annual pro-forma R&D budget of about £2.1bn (€2.5bn).
"We are pleased to receive such strong support from our shareowners," said Monsanto chairman and chief executive officer Hugh Grant.
"By bringing together our expertise and resources we can do more together to benefit growers around the world and help address broad global challenges like climate change and food scarcity."
Bayer chief executive officer Werner Baumann said: "The acquisition is driven by our belief this combination can help address growing challenges facing the overall agriculture industry."
Bayer first made a play for Monsanto back in mid-May, an offer that was quickly rejected by Monsanto, prompting Bayer to raise its all-cash offer by $3 to $125 per share.
Monsanto directors held firm and described the takeover bid as "financially inadequate and insufficient to ensure deal certainty".
However, this week's agreement, adding another $3 to the share worth, will unite two "different, but highly complementary businesses", according to both multinationals.
On completion of the deal the combined agriculture business will have headquarters in Monheim in Germany, Missouri, North Carolina and San Francisco, with other offices around the world.