Yamaguchi was born in Kōchi, Kōchi, Japan. She attended Joshibi University of Art and Design where she studied industrial design. Yamaguchi joined Sanrio in 1978. In 1980 she became the third Hello Kitty designer. She has been the main Hello Kitty designer for much of the character's history.
- Jonathan Clements. Schoolgirl Milky Crisis: Adventures in the Anime and Manga Trade. A-Net Digital LLC. p. 285. ISBN 978-0-9845937-5-0. Retrieved 25 March 2012.
- Takagi, Jun (August 21, 2008). "10 Questions for Yuko Yamaguchi". TIME Magazine. Retrieved 2009-10-31.
- Tabuchi, Hiroko (May 14, 2010). "In Search of Adorable, as Hello Kitty Gets Closer to Goodbye". NYTimes.com.
- "ジュエルペット映画版で芦田愛菜がお菓子の国のプリンセスに！". Movie Collection. April 2, 2012. Retrieved September 23, 2012.
- Official blog (in Japanese)