The mood of "The Nightingale and the Rose" is initially whimsical and romantic but becomes sadder and more cynical by the end. At the beginning of the story, readers are immersed in a romantic fairy-tale landscape where birds converse with trees and the biggest sorrows have to do with broken hearts. The Student, for instance, is a woebegone lover whose happiness depends on finding a red rose to give to his lover. The Nightingale describes him like this:
"Here at last is a true lover... Night after night have I sung of him, though I knew him not: night after night have I told his story to the stars, and now I see him. His hair is dark as the hyacinth-blossom, and his lips are red as the rose of his desire; but passion has made his face like pale ivory, and sorrow has set her seal upon his brow."
The references to "desire" and "passion"—and the bold declaration that the Student is a "true lover"—sets the story up to be a dramatic romance about the pursuit of true love. This sense of romance and heightened drama continues with the Nightingale's quest to find the rose.
However, the mood of the story soon changes when the Student presents the rose to the girl. While this point is built up to be the tale's culmination, the girl's quick dismissal of the rose subverts the expectations of a straightforward love story and quickly dispels the romantic mood. The Student's immediate turn to anger rather than sadness—as he calls the girl "ungrateful" and throws the rose into the gutter—presents him as a petulant youth rather than as a heroic lover. After his rejection, the story ends with the Student's cynical reflections:
"What a silly thing Love is," said the Student as he walked away. "It is not half as useful as Logic, for it does not prove anything, and it is always telling one of things that are not going to happen, and making one believe things that are not true.
By the end of the tale, the "true lover" has quickly become a cynic who scoffs at the uselessness of love. The story thus takes on a much more pessimistic, sour mood. To that end, the Student's disregard for the rose, which cost the Nightingale her life, adds a certain sense of sadness, giving the end of the story a rather somber feeling.