A memorial stone to The Chronicles of Narnia creator will be unveiled later, to mark the 50th anniversary of his death.
He is the first Belfast writer to receive such an honour.
Lewis will join such greats as Charles Dickens, Oscar Wilde, John Keats, William Blake and TS Eliot in a tradition going back 600 years.
It coincides with a day of literary celebration in Belfast, that includes a CS Lewis mayoral reception at the city hall.
The event is part of the week-long CS Lewis festival designed to celebrate and enjoy the work and life of one of Belfast's greatest literary sons.
Belfast Lord Mayor MÃ¡irtÃ­n Ã“ Muilleoir said:  "I feel honoured to host a reception for the finest modern Belfast writers, who follow a proud local literary heritage which the likes of CS Lewis helped to build.
"It is also fitting that the best Belfast writers should get together to read on the very day that CS Lewis is interred in Poets corner in Westminster Abbey - the first ever Belfast writer to receive that honour.
"This is a great day for our city and our wealth of writers past and present".
Lewis (1898-1963) is best remembered for writing The Chronicles of Narnia, a series of books that has sold more than 100m copies worldwide.
The Lion, the Witch and the Wardrobe, the first instalment in the saga, was published in 1950 and has been adapted since for stage, TV and film.
Other works by the Belfast-born novelist, essayist and literary critic include The Screwtape Letters, The Space Trilogy and the non-fiction titles Mere Christianity and Miracles.
Former poet laureate Ted Hughes was the most recent writer to be commemorated at Westminster Abbey with a posthumous memorial stone.
Belfast-born writer and scholar CS Lewis is to be officially inducted into Poet's Corner in Westminster Abbey.