Baucus was born on December 11, 1941 in Helena, Montana. He studied at Stanford University. Baucus was married to Ann Geracimos from 1982 until they divorced in the same year. Then he was married to Wanda Minge from 1984 until they divorced in 2009. He has been married to Melodee Hanes since 2011. He has one son, Zeno, with Geracimos.