The pick is a bet that an energetic younger leader will help the party capitalize on the historic enthusiasm that swept Obama to his landslide win.
Kaine, like Obama a graduate of Harvard Law School, was among the earliest statewide officials to endorse Obama, and was among finalists to be the vice presidential candidate on his ticket.
Kaine has long one of the party's rising younger stars, even delivering his party's nationally televised response to one of President George W. Bush's State of the Union addresses.
The governor won handily in a traditionally Republican state in part with frank conversation about his Roman Catholic faith. His victory in the state's exurbs is viewed as a model for other Democrats.
Kaine is a former mayor of Richmond and formerly was a public-interest lawyer who took capital cases.
Kaine's fervent backing was one of the reasons Obama was long given a chance of winning the Old Dominion, which has voted consistently Republican in presidential races. Obama wound up beating Sen. John McCain (R-Ariz.) handily.
Kaine, who will be 51 in February, graduated from the University of Missouri, and took a year off from Harvard Law to serve as a missionary in Honduras. In 2001, he became lieutenant governor under former governor Mark Warner.
Kaine received high marks for his handling of the national spotlight following the mass slayings at Virginia Tech in 2007.
The governor and his wife, Anne Holton, a Harvard law graduate and daughter of former Virginia Gov. Linwood Holton, have three teen-age children.