In her professional life, Matienzo worked on reform in the public school system in Puerto Rico in order to extend education to all classes of children.
The Puerto Rican Feminine League, the first organization of its type to work for women's rights, was founded in 1917 by women of the "propertied, professional and intellectual elite", including Ana Roque de Duprey, Ángela Negrón Muñoz, and Matienzo, who were all teachers.
In 1921, Carlota Matienzo was one of the founders as the group changed its name to the Suffragist Social League and began to work directly for women's voting rights.
[4] After allying with the Popular Feminist Association of Working Women of Puerto Rico, the League supported universal suffrage.
[1][5] Matienzo Román continued as one of the League's prominent members until 1924, when it divided into two organizations, split largely along grounds of political party affiliation of its leaders.