Educated initially at the Los Angeles Normal School, now known as the University of California, Los Angeles, Lou transferred to and graduated in 1893 from San Jose Normal School, now known as San Jose State University, with a teaching certificate. She went on to study at Stanford University, where she met Herbert Hoover. In 1898 Lou graduated, gaining a B.A. in Geology.
Herbert Hoover and Lou Henry were married in 1898 and honeymooned in Shanghai, China. They lived in China from 1899 until August 1900. While in China, Lou studied the Mandarin Chinese language.
During The First World War, Lou helped her husband provide relief for Belgian refugees. For her work, she was decorated in 1919 by King Albert I of Belgium. She was also involved with the American Women's War Relief Fund, which provided ambulances, funded two hospitals and provided economic opportunities for women during WWI.