Bosses say the latest contribution to the Foundation 2020 initiative will help ensure future generations can enjoy the Romanesque landmark.
The Very Rev Andrew Tremlett, Dean of Durham, said: "Sharing our faith and heritage with the world is a fundamental part of the Cathedral's vision.
"Conservation and repair of this wonderful building is crucial to this vision. We are extremely grateful to the Heritage Lottery Fund for its continued support of Durham Cathedral."
Interior of Durham Cathedral
Foundation 2020 hopes to raise £10m by 2020. The Cathedral has already invested £3.7 million into the fund.
The new grant is coming from the Heritage Lottery Fund (HLF), which is supported by players of the National Lottery. It is available to match donations raised on a £1 per £1 basis; bosses hope this will see more funds raised.
Ivor Crowther, Head of HLF North East, said: "Thanks to money raised by National Lottery players, we're pleased to help kick-start Durham Cathedral's ambitious fundraising campaign to enhance their long-term financial resilience and ensure the incredible heritage of the cathedral remains safe and accessible for all."
Another lottery-supported project at Durham Cathedral, Open Treasure, involves the Anglo-Saxon Treasures of St Cuthbert installed at their new permanent home - the 14th century monastic Great Kitchen.
The UNESCO World Heritage Site attracts 750,000 each year.