The Preschool version of the Dimensions of Mastery Questionnaire (DMQ-18) is a popular instrument to assess children's ability to master the environment through action or activity to explore, influence, or control the physical atmosphere. Although this instrument was originally developed in English, it has now been translated and validated in five other languages: Hungarian, Turkish, Chinese, Spanish, and Persian. As we notice a growing interest in research on the mastery motivation among Bangladeshi preschoolers, we have taken this effort to translate and validate the DMQ-18 and explore the factor structure of the Bangla version of this questionnaire. After translating all 39 items of the questionnaire into Bangla, it was administered on 206 children, aged 3 to 6 years, recruited randomly from ten preschools in Dhaka. The schools were selected randomly from the official list of preschools prepared by the Dhaka City Corporation. Class teachers of the respective children completed the questionnaire with the assistant of research assistants. The Bangla version of the questionnaire retained all 39 items, with seven factors as they were in the English version. The Bangla version shows sufficient reliability (Cronbach's alpha = 0.87; test-retest reliability = 0.89 for whole questionnaire and .79-.89 for sub-scales; inter-rater reliability = 0.88 for whole questionnaire and .79-.88 for sub-scales), and validity (correlated positively with the English version; r = 0.85). Due to its robust psychometric properties, the Bangla DMQ-18 is suggested to be used for Bangladeshi preschool children to assess their mastery motivation.