Spencer Perceval was shot by John Bellingham on May 11 1812, in the lobby of the House of Commons on his way to attend an inquiry into the recent Luddite riots.
It is said his last words were: "Oh, I have been murdered."
Four patterned floor tiles in Parliament said to mark the spot where Perceval fell were removed during recent renovation, leaving the historic event lacking a commemoration in the Palace of Westminster.
But Michael Ellis, Conservative MP for Northampton North, took up the case in the Commons for a replacement as Perceval was previously a member for Northampton.
And he has now secured support from the parliamentary authorities for a plaque to be placed on the wall in St Stephen's Hall, near to the location thought to mark the spot.
Mr Ellis said: "It's an important part of the history of Northampton in Parliament but also an important part in the history of this country - the only British prime minister to be assassinated, 202 years ago.
"There's also a sort of a fascinating quirk of history that the current MP for North West Norfolk, Henry Bellingham, is actually a descendant of the assassin who shot Perceval.
"It's important to mark out history and this is one small way of doing that.
"It doesn't cost much and it will be a talking point for future generations because Parliament is a busy workplace and the mother of Parliaments and our legislature; it's also a popular tourist destination."