Background: As delays or disorders in early language and communication are the most prevalent symptom in children with disabilities, early screening is crucial to promote prevention, early diagnosis, and intervention. However, to the best of our knowledge, no screening tool is available for the joint assessment of early language and social communication skills in European Portuguese (EP)-learning children, which is critical for screening, monitoring and enrolment in appropriate early intervention services. Aims: (1) To adapt and validate the EP version of the Communication and Symbolic Behaviour Scales Developmental Profile™ (CSBS DP™) Infant-Toddler Checklist, a parental report for the screening of early language and social communication skills. (2) To conduct a cross-cultural comparison between the EP adaptation and the original US version. Methods & Procedures: A total of 611 EP-learning children (ages 6-24 months) were assessed on the CSBS DP Infant-Toddler Checklist. Normative data, psychometric characteristics (i.e., internal consistency and test-retest reliability), and cross-cultural comparison between the EP and the original version were explored. Outcomes & Results: Internal consistency ranged from good to excellent and the test-retest reliability was excellent. The performance of the EP and US samples matched on almost all scores. However, EP children performed significantly better than their American peers in the Social compositive at 22 months and in the Symbolic composite at 20 months. No further differences were found. Conclusions & Implications: These findings showed that the EP CSBS DP Infant-Toddler Checklist seems to be a reliable screening tool of communicative and symbolic behaviours for EP-learning children, which can be particularly relevant for decision-making in clinical practice.