Abstract: From 1940 onward, Henri Guillemin (1903-1992) was a propagandist for Paul Claudel’s work. It was only in 1968, after Claudel’s death, that he published his study, Le « Converti » Paul Claudel, where he distances himself from a certain orthodox critical response to Claudel. The correspondence that Guillemin presents, consisting of sixty two letters—plus a report about a personal encounter and little-known secrets—allows us to take a more careful look at a complex relationship while letting us appreciate Claudel’s exceedingly significant voice.