Delgado returned to the Philippine Islands in 1908 and joined the Philippine Government as a law clerk. Later, he became the chief of the law division of the executive bureau, serving until 1913 when he resumed private law practice. In 1918, Delgado served in the Philippine National Guard and became a member of the National Council of Defense for the Philippines. From 1931 to 1935, he served in the Philippine House of Representatives for
Bulacan's 1st district as a Nationalist. He was elected as a
Resident Commissioner to the United States and served from January 3, 1935, until February 14, 1936, when a successor qualified under the new government of the
Commonwealth of the Philippine Islands. Delgado was appointed as a justice of the court of appeals in February 1936, serving until 1937. He then resumed his law practice and became a delegate to the International Committee of Jurists in
Washington, D.C., and to the United Nations Conference in
San Francisco, California in April 1945. Delgado was a member of the Philippine War Damage Commission from June 4, 1946 to March 31, 1951. Subsequently, he served as a
Senator from 1951 to 1957. Finally, Delgado held the position of Ambassador to the
United Nations from September 29, 1958 to January 1, 1962. ==Achievements==