Vocabulary size has been repeatedly shown to be a good indicator of second language (L2) proficiency. Among the many existing vocabulary tests, the LexTALE test and its equivalents are growing in popularity since they provide a rapid (within 5 minutes) and objective way to assess the L2 proficiency of several languages (English, French, Spanish, Chinese, and Italian) in experimental research. In this study, expanding on the standard procedure of test construction in previous LexTALE tests, we develop a vocabulary size test for L2 Portuguese proficiency: LextPT. The selected lexical items fall in the same frequency interval in European and Brazilian Portuguese, so that LextPT accommodates both varieties. A large-scale validation study with 452 L2 learners of Portuguese shows that LextPT is not only a sound and effective instrument to measure L2 lexical knowledge and indicate the proficiency of both European and Brazilian Portuguese, but is also appropriate for learners with different L1 backgrounds (e.g. Chinese, Germanic, Romance, Slavic). The construction of LextPT, apart from joining the effort to provide a standardised assessment of L2 proficiency across languages, shows that the LexTALE tests can be extended to cover different varieties of a language, and that they are applicable to bilinguals with different linguistic experience.