Background: Retirement may cause some problems in people and cause incompatibility and symptoms called retirement syndrome.Objectives: The present study was conducted with the aim of investigating the effect of existential therapy on the feeling of helplessness and failure, the feeling of old age and emptiness, and the feeling of confusion and conflict in retired teachers.Methods: This study was semi-experimental with a pre-test and post-test design with a control group. The statistical population included all retired teachers in Kermanshah, Iran. Among them, 40 teachers were selected by available sampling method and randomly assigned into two experimental and control groups. The participants completed the retirement syndrome questionnaire in two phases: pre-test and post-test. Multivariate covariance analysis method was used to analyze the data.Results: There is a difference differences between the retired teachers of the existential therapy group and the retired teachers of the control group in the variables of feelings of helplessness and failure (p=0.0001, f=10.11), feelings of aging and emptiness (p=0.0001, f=10.10) and feelings of confusion and conflict (p=0.0001, f=10.11). Existential therapy led to a decrease in the mean score of the participants of the experimental group in the variables of retirement syndrome.Conclusion: The current findings showed that the holding of existential therapy sessions had a positive effect on reducing the symptoms of retirement syndrome in retired teachers, and with the training of existential therapy in old age, it is possible to deal with or reduce the symptoms of retirement syndrome by creating preparation for retirement.