Lewis's publisher, Geoffrey Bles, allowed him to choose the illustrator for the novel and the Narnia series. Lewis chose Pauline Baynes, possibly based on J. R. R. Tolkien’s recommendation. Baynes had greatly impressed Tolkien with her illustrations for his Farmer Giles of Ham (1949). However, Baynes claimed that Lewis learned about her work after going into a bookshop and asking for a recommendation for an illustrator who was skilled at portraying both humans and animals. In December 1949, Bles showed Lewis the first drawings for the novel, and Lewis sent Baynes a note congratulating her, particularly on the level of detail. Lewis’s appreciation of the illustrations is evident in a letter he wrote to Baynes after The Last Battle won the Carnegie Medal for best children’s book of 1956: "is it not rather 'our' medal? I’m sure the illustrations were taken into account as well as the text".
The British edition of the novel had 43 illustrations; American editions generally had fewer. The popular United States paperback edition published by Collier between 1970 and 1994, which sold many millions, had only 17 illustrations, many of them severely cropped from the originals, giving many readers in that country a very different experience when reading the novel. All the illustrations were restored for the 1994 worldwide HarperCollins edition, although these lacked the clarity of early printings.