Spirituality is a basic human drive with diverse forms of expression that make for unique patterns of thinking consonant with an advanced level of cognition and integration of information. The paper features the Humanistic Spirituality Model, which captures the essential dimensions of humanistic spirituality through three components: self-actualisation, transcendence and ultimate meaning in life. The Humanistic Spirituality Inventory (HSI), a measure of spirituality developed on the basis of the Humanistic Spirituality Model, contains three scales corresponding to the three model components. According to the results of the HSI validation study (N = 331), the instrument has good psychometric properties, i.e. adequate content and construct validity as well as satisfactory internal consistency and test-retest reliabilities, which makes it a proper spirituality research measure.