Introduction: Watching television (TV) is a popular pastime among Iranian children to the extent that it has been attributed to the rise of childhood obesity. The present study investigated the validity and reliability of a questionnaire on television watching of preschool children from the perspective of parents. Methods: A total of 114 mothers of children aged 2-6 years from 10 preschools in District 2, Tehran City, recruited by convenience, were interviewed after receiving their consent. The questionnaire consisted of 23 questions and two subscales on the amount of time and the perceived impact of watching TV. The validity (content and construct) and reliability (test-retest and internal consistency) of the questionnaire were analysed using SPSS (version 21). Results: Out of the original 23 questions, only 11 questions that met the criteria of the content validity ratio (CVR) and content validity index (CVI) were selected and internal correlation of each subscale with total score was calculated and found to be satisfactory (0.566 and 0.685 respectively). Intraclass correlation coefficient was between 0.796 and 0.889 and Cronbach’s alpha was between 0.887 and 0.941. Conclusion: Overall, the validity of the questionnaire developed for this study was found to be satisfactory. This questionnaire could be applied in similar settings using larger sample sizes.