According to the Nationality Law (Law nr. 37/81, of October 3), it is possible for the parents of a child born in Portugal to obtain Portuguese nationality.
For such purpose, some requirements must be fulfilled, among them, the individuals applying for nationality must be ascendants (father or mother) of an original Portuguese citizen, that is, the child must have been born in Portuguese territory.
In addition, at the time of the application, it is necessary that the applicant parent is residing in Portugal and fulfils the time requirement of at least five years of residence in the country.
It is important to clarify that the law establishes a minimum period of residence of five years “regardless of the title”, that is, if the individual has remained in Portugal without a residence title or in an irregular manner, he may still apply for nationality, if he presents documents that effectively prove his residence during five years in the country.
Finally, it is also required that the ascendency was established at the moment of the birth of the Portuguese citizen, otherwise, the progenitor will not be able to request nationality by this means.