Explanation
Yes. Portuguese is Brazil's primary language in the sense that it is the country's most widely spoken language. It is also the official language.
Brazil's National Institute of Historic and Artistic Heritage explicitly identifies Portuguese as both official and most widely spoken. EBSCO's independently published country reference gives the same description.
This does not mean Brazil is exclusively Portuguese-speaking. Its national linguistic inventory recognizes a diverse landscape that includes Indigenous, immigrant, sign, Creole and Afro-Brazilian languages, alongside regional varieties of Portuguese.
Key takeaway
Portuguese predominates in Brazil, but the country has a much broader linguistic heritage.