Practical adherence to the inner etiquettes of prayer is a central concept in Islam, extensively emphasized in the Qur'an and Hadith due to its profound impact on various aspects of human life. This study aimed to develop and validate a questionnaire designed to assess practical commitment to the inner etiquettes of prayer, grounded in Islamic teachings. A mixed-methods design was employed across two phases. In the first phase, qualitative content analysis following the conventional model by Hsieh and Shannon (2005) was conducted to extract components and generate preliminary items from Islamic texts, including Qur'anic verses and Prophetic traditions. In the second phase, the questionnaire was administered to a stratified random sample of 260 seminary and university students to evaluate its psychometric properties. Content validity was assessed by five experts in Islamic studies and psychology using the Content Validity Ratio (CVR ≥ 0.99) and the Content Validity Index (CVI ≥ 0.79). Exploratory factor analysis supported the construct validity, identifying two main components: "Inner Etiquettes of Preparatory Acts of Prayer" and "Inner Etiquettes of Concurrent Acts of Prayer." The instrument demonstrated strong internal consistency, with a Cronbach’s alpha of 0.888 and a Guttman split-half coefficient of 0.867. These findings suggest that the instrument possesses robust psychometric characteristics and can be effectively employed in academic research exploring the religious dimensions of Islamic prayer.