[3] Kalaw served as secretary of then Philippine Assembly Majority Floor Leader Manuel L. Quezon until 1908.

In October 1908, Interior Secretary Dean C. Worcester filed a libel suit against the paper for their editorial entitled "Aves de Rapiña" ("Birds of Prey").

[3][5] In 1909, Kalaw was elected the youngest member of the Philippine Assembly at age 25, representing Batangas's 3rd district.

During his term, he sponsored bills supporting internal migration and agricultural development and maintenance of public schools through municipal taxation.

[7] Kalaw was a member of the Academy of Political Science, American Social and Political Science; Sociedad Americana de Derecho Internacional; Real Academia Hispano Americano de Ciencias y Artes, of whose Philippine Section he became president in 1925; Associacion Hispano-Filipina, and the Philippine Library Association.

Their son, Teodoro Kalaw Jr., became a prominent businessman and was married to Philippine senator Eva Estrada.