Purpose To date, there is no tool for assessing early pragmatic development of Polish-speaking children. This study aimed to adapt to Polish a standardized parent report measure, the Language Use Inventory (LUI; O'Neill, 2009, in order to enable cross-cultural comparisons and to use the LUI-Polish to screen for pragmatic development in children 18-47 months of age. We concentrated on the sociocultural and functional adaptation of LUI and aimed to demonstrate its reliability, developmental sensitivity, and concurrent validity. Method Parents completed an online version of LUI-Polish, longitudinally at 3 time points (when the child was 20, 32, and 44 months old). In addition, parents completed the Polish adaptations of the Questionnaire for Communication and Early Language at 22 months and the Language Development Survey at 24 months. Children's spontaneous speech was assessed at 24 months, and their expressive and receptive vocabulary was assessed at 36 months. Results All 3 parts of the LUI-Polish (Gestures, Words, and Sentences) showed very good levels of internal consistency at each time point. Significant correlations were observed between all parts of the LUI-Polish at all 3 measurement time points. The expected developmental trajectory was observed for boys and girls providing evidence of its developmental sensitivity for children between the ages of 2 and 4 years: an increase with age in the total score (due to an increase in Words and Sentences) and a decrease in Gestures. Supporting concurrent validity, significant correlations were found between children's performance on (a) the LUI-Polish at 20 months and the Questionnaire for Communication and Early Language at 22 months as well as the Language Development Survey and spontaneous speech measures at 24 months and (b) the LUI-Polish at 32 months and the 2 measures of vocabulary comprehension and production at 36 months. Conclusion The Polish adaptation of the LUI demonstrated good psychometric properties that provide a sound basis for cross-cultural comparisons and further research toward norming of the LUI-Polish. Moreover, the expected developmental trajectory in the pragmatic development of Polish children was observed.