Ah Jook Ku was born on April 24, 1910, in Kailua, Hawaii. She was one of 15 children in her family. She and her family grew up on the 'Ewa Plantation in Hawaii, where her father worked as a luna. Ku was Chinese American, a descendant of early Chinese immigrants to Hawaii. She attended Mid-Pacific Institute on a scholarship. Ku served as a high school reporter for the Honolulu Star-Bulletin while at Mid-Pacific. She earned a degree in education from the University of Hawaii in 1933. Following graduation from college, Ku graduated from the University of Missouri School of Journalism in 1935, also on a scholarship. She was only the third woman of Chinese descent to graduate from the School of Journalism. Additionally, she became only the second Hawaiian "exchange student" to graduate from the journalism school. Ku was often involved with various university journalism clubs while in college. She often appeared on campus radio broadcasts and before community groups as an advocate for Hawaii. Despite her academic achievements, Ku's parents believed that girls did not deserve an education. She often recounted a story about how her father once considered selling her for a single bag of rice. Ku commented on her father's attitude towards education, "the head of the family wasn't eager about educating women."
Ah Jook Ku became executive director of the Honolulu Community Media Council in 1975, the same year that she retired from the Department of Education. The council had been founded as a nonprofit volunteer group in 1970. The group was created in response to a ban on reporters from the Honolulu Star-Bulletin and Honolulu Advertiser from press conferences by then Honolulu mayorFrank Fasi. Its purpose was to promote accurate and ethical journalism within Hawaii, support First Amendment rights and seek transparent public access to government information. Ku remained involved with the Council as executive director for 25 years. Ku was especially active in the 1980s, fighting on behalf of Hawaii's sunshine law. She retired from the Council in 2002. Ku was an original founding member of a group called "Save Our Star-Bulletin" in the late 1990s. The group was formed in response by an attempt by Liberty Newspapers, the former owner of the Honolulu Star-Bulletin, to shut down the newspaper in 1999. The "Save Out Star-Bulletin" sued Liberty Newspapers in U.S. federal court and successfully blocked the closure of the Star-Bulletin.
Ah Jook Ku died on Monday, August 6, 2007, at Leahi Hospital in Honolulu. She was 97 years old. She was survived by a sister, Yuk Jun Joseph, and several nieces and nephews. Her funeral was held on August 21, 2007.