The linguistic profile of bilingual children is known to show areas of overlap with that of children affected by Developmental Language Disorder (DLD), creating a need to differentiate the profiles and provide clinicians with tools to evaluate bilingual speakers in both of their languages. Data from typical adult bilinguals provide a picture of the language of a bilingual speaker at the end of language development. The present work explores how clitic production and nonword repetition (NWR) behave in mature language systems in situations of bilingualism, aiming to provide initial data as a benchmark on Italian as a non-dominant language. Heritage speakers (HSs) of Italian were confronted with adult immigrants (AIs) who moved from Italy to an English-speaking country in adulthood. Clitic pronouns were found to be vulnerable in HSs, who produced approximately 35% of the target clitics against the 80% of Ais, suggesting that clitic pronouns may not be reliable structures to test language competence in heritage Italian. On the other hand, HSs were >97% correct in NWR, suggesting that this paradigm should be explored as a possible marker to test language competence in these populations.