The institute declared it will use the extra cash to expand its network globally, increase its number of accredited trainers and grow its innovation unit to build services and tools, such as its Open Data Certificates.
The ODI aims to support companies in exploiting open data and works with the UK government to make public datasets available online. The organisation was co-founded by worldwide web inventor Sir Tim Berners-Lee, who is now ODI president.
Omidyar Network policy director Martin Tisné said the ODI is an "ambitious global network" which covers the open data value chain from the supply to the demand side.
“The ODI plays a crucial role in building the case for open data in business," he said. "They have made great progress over the past two years and it is important that this momentum is maintained and built upon.
"In entering a further three-year agreement, Omidyar Network looks forward to supporting the ODI in its work to release the power of open data to address local and global issues.”
More on open data
The Omidyar Network was set up by eBay founder Pierre Omidyar and his wife Pam in 2004. Omidyar previously provided $750,000 at the ODI's launch in late 2012 to support its early development.
The funding announcement coincided with the ODI’s second annual report. The institute said it has trained more than 700 people and increased its member network to more than 100 businesses and organisations. It has also supported 22 franchise organisations, which it calls nodes, in 15 countries, including five in the UK.
The ODI said it has “unlocked £16.6m of value in 2014 for the open data ecosystem, including growing income by £1.9m”. This is on a rough par with a £2m-per-year contribution it gets from government organisation Innovate UK.
The ODI also said it has supported 18 businesses through its startup programme, with the first two cohorts now employing 70 people and securing £4m in contracts and investment.
ODI CEO Gavin Starks thanked supporters, members, partners and funders for helping the ODI become a "global agent for change" so quickly.
"With their help, we are demonstrating that open data is broad and deep in its influence," he said.
"Businesses are seeing open data as a competitive advantage, governments are revealing insights and efficiencies, and startups are paving the way in the data innovation landscape across all sectors.”