Adults distinguish sarcasm from literal language according to intonation involving a reduction in fundamental frequency (F0). We examined whether children's and adults' interpretation of a sarcastic speaker's belief, attitude, and humor was affected by degree of F0 reduction by presenting five- to six-year-olds and adults with sarcastic and literal criticisms with a small, medium, or large mean F0 reduction. Children and adults were more accurate in attributing the speaker's belief and intent for sarcastic criticisms for large F0 reductions compared to small reductions. These results show that F0 reduction is a helpful cue to sarcasm interpretation for both children and adults.