Introductoin: The purpose of present research was to design Existential anxiety questionnaire (death, freedom, loneliness and meaninglessness) and investigate its validity and reliability. The research design was exploratory study of instrumentation and validity assessment.
Method: This research consisted of three stages. The first stage was to investigate the theoretical foundations and conceptual frameworks of existential anxiety. The second stage was to construct a Questionnaire for Existential Anxiety and evaluate its content validity and the third stage involved expanding validation and assessing reliability of questionnaire. To evaluate the validity and reliability, 505 employees and students of 5 Tehran universities were selected as sample using multi-stage cluster sampling. Research tools included Demoralization scale (translated by Naghiyayi and Bahmani, 2013) and Collett- Lester Death Anxiety scale (1990) that estimate concurrent and convergent validity and Existential Anxiety Questionnaire. All the subjects replied to two scales.
Results: Findings showed that according to 10 expert opinions, Concurrent validity was. 0.95 by ICC and Concurrent validity and convergent validity was obtained 0.82 and 0.95, respectively. Exploratory Factor Analysis and Varimax factor rotation indicated Questionnaire theoretical structure consists of 4 factors that factors nominated according to theoretical base. Confirmatory factor analysis also indicated the goodness of fit for these factors.  Furthermore the Cronbach's alpha and test-retest reliability was 0.82 and 0.86, respectively.
Discussion and Conclusion: It can be concluded that a standard Questionnaire with 29 items and 4 subscales is available for evaluating Existential Anxiety in Persian.