<p>The Penn State Worry Questionnaire for Children (PSWQ-C), developed by Bruce F. Chorpita, is a tool used worldwide for evaluating worry in children. The original US English PSWQ-C has been translated into several other languages and there is support for good psychometric properties of the original and several translated versions. However, the cross-cultural measurement equivalence of the PSWQ-C has not been tested yet. The aim of this study is to evaluate the measurement invariance of the PSWQ-C scale across Poland and the US. This study examines the measurement invariance of the PSWQ-C between Poland and the US— analyzing data from samples of children in Poland, responding to the Polish adaptation of the PSWQ-C (<i>N</i> = 199), and children in the US, responding to the original US English PSWQ-C (<i>N</i> = 199). Data analysis involved two steps. The first step was to test the factor structure of the PSWQ-C in the original US English and Polish versions. Subsequently, multigroup confirmatory factor analysis was conducted to compare three levels of measurement equivalence (configural, metric, and scalar) across the two samples from Poland and the US. The results indicate that the bifactor model is the most appropriate model for the data in both groups. Nevertheless, when considering the entire group, the one-factorial model meets the acceptability criteria, demonstrating equivalence at all levels of measurement. The cross-cultural measurement invariance of the Penn State Worry Questionnaire for Children has been demonstrated across Poland and the United States of America.</p>