Ambiguity tolerance is an individual trait indicating low aversion to ambiguity that is closely related to creativity. Appreciation and discussion of art are known to improve ambiguity tolerance, but the effects of appreciation and discussion have not been studied separately. In this study, we used haiku poetry with the characteristic of ambiguity to confirm the effect of appreciation by separating it from the discussion. Additionally, we conducted haiku creation to examine the effect of creation. To this end, 137 participants answered the ambiguity tolerance scale at five time points: before and after haiku appreciation and creation, and 1 week later. We also used the Multidimensional Attitude toward Ambiguity Scale, which organizes ambiguity tolerance into three subfactors. These subfactors are discomfort with ambiguity, absolutism, and the need for complexity and novelty, which correspond to the affective, cognitive, and epistemic aspects of ambiguity attitudes, respectively. The results showed that absolutism, which is the cognitive aspect of ambiguity tolerance, decreased after the appreciation and creation of haiku, and this effect persisted after 1 week. This result indicates that cognitive changes such as the acceptance of ambiguity can occur through the appreciation and creation of haiku, which require various interpretations and choices.