Objective: to understand the existential experience of children undergoing chemotherapy on the importance of playing. Methods: qualitative research performed in the outpatient clinic of a teaching hospital with five children undergoing chemotherapy. Data were collected through the interviews and analyzed in the light of the Humanistic Nursing Theory. Results: the discourses revealed the children's understanding of their illness and their treatment, evidencing the deprivations experienced by them and the situation of emotional imbalance. Playing, according to the children's reports, elicited positive feelings and represented a way for time to pass faster. Conclusion: the chemotherapy treatment was considered ambiguous, being an unpleasant experience, but necessary for cure. The games in the outpatient chemotherapy service were a viable tool to deal with the discontent before the situation lived, provoking positive feelings such as happiness and satisfaction.