Law degree from the University of La Coruña (1997) and doctor from the same university with the thesis The protection of the victim in the criminal process. He was substitute magistrate of the Provincial Court of Lugo. He is a professor of Procedural Law at the University of La Coruña.

He is the author of more than fifty bibliographical references, participated in different research projects and gave numerous conferences. Between his works highlight those referring to civil and social rights, those opposed to the privatization of the University and the Bologna Plan or those aimed at improving the protection of victims of macho violence Ferreiro speaks four languages ​​(Galician, Spanish, English and German) and is a member of Deportivo since 1993. The success of the popular candidacy of the Atlantic Tide Popular Unity in the Elections of May 24, 2015 made him mayor of A Coruña.