The Charles Dickens Museum in London has been given the grant to buy the desk and chair, which has always been in private ownership.
They had been passed down through the Dickens family after his death in 1870, but were auctioned for the Great Ormond Street Charitable Trust in 2004.
Dickens used the desk in his final home in Gad's Hill Place in Kent.
Our Mutual Friend and his unfinished novel The Mystery of Edwin Drood were also penned at the desk.
The furniture would have been sold at public auction if it was not for the grant from the  National Heritage Memorial Fund (NHMF).
Made famous in two paintings begun the year he died, the Empty Chair by Luke Fildes and Dickens' Dream by RW Buss, the desk and chair are already on display at the Charles Dickens Museum at the author's former home.
Robert Moye, director of the Charles Dickens Museum, said: "We are delighted to have been able to acquire Charles Dickens' iconic writing desk and chair for permanent display in his study at 48 Doughty Street.
"They hold a unique place in our literary heritage and, as we embark on our exhibition exploring The Mystery of Edwin Drood, it is timely that the desk he used when writing his final novel has been secured for the benefit of all our visitors."
The desk where Charles Dickens wrote Great Expectations is finally on public display thanks to a £780,000 grant.