Senator Ramon Diokno was born in Taal, Batangas on March 28, 1886 to Ananias Diokno and Paulina Mara Cigan, He received his primary instruction from his native town and continued his studies in a private school in Manila and in Colegio de San Antonio de Padua under Ignacio Villamor. He was admitted to the practice of Law in April, 1905. While he was student he organized the Asociacion Escolar de Filipinas and was chosen its first president. He founded the Colegio la Ilustracion, and was one of the founders of the Rizal University, where he became professor. He was editor of La Fraternidad and El Nacionalista and was president of the Union del Trabajo de Filipinas and honorary president of Union de Marinus de Filipinas. He was initiated as a Mason in Sinkuan Lodge and was named to reorganize the Hilad Lodge and was workshipful master for two years. He was also one of the founders of the Gram Logia Regional de Filipinas.
He won in the special election for city councilor for the Northern District of Batangas in 1918 and again in 1933. In the first Commonwealth election held on September 17, 1935, he was one of the chief campaign managers of President Quezon and was immediately appointed Corporate Counsel.
He was senator from 1946-1949.
He was also corporate counsel for the Philippine National Bank, Manila Railroad Company, Manila Hotel Company, National Loan and Investment Board, Metropolitan Water District, National Development Company, Cebu Portland Cement Company and National Produce Exchange.
He married Leonor Wright with whom he had 10 children.